TobiMikami's Guide on basic GFX tips!
This document will not teach you in and out GFX, nor will it make your GFX anything great, but it will provide advice and tips that may save you time or give you a solution to a problem. These tips are not guaranteed to be efficient, but they get the job done for the average n00b. 

1. Recommendations
This guide's tips are based for users of Tile Layer Pro, the program is free and easily downloaded from the Metroid Construction website. I also suggest in correlation with TLP, GIMP 2.9 (At least I beleive it's 2.9 they're on as of August 2014) It's a bit excessive for what you're doing, but it's well worth it, got more tools then you'll need plus some. It's a free download versus paying for Photoshop which is just as confusing and does a hell of a lot more than MS Paint. Of course you're also going to need SMILE, if you don't have SMILE you shouldn't even be thinking about this guide, let alone any type of GFX yet. This guide is classified as an Intermediate work, you need to know the basics to use this, however, these tips are pretty basic, just stuff people don't really think about.

2. Ripping palettes. 
Palettes can be confusing. For the average noob, this is what you want to remember:
-There are 7 "used" palettes in most of the tilesets you can rip from SM
-To rip Palettes, go into SMILE, Tools, Graphics Editor. Then under the graphics subscreen, go to Palette, Export. Congrats, you did one of the most basic functions in the SMILE graphics editor! Have a cookie to celebrate!
-You should also rip the GFX for this area as well, same as before to get into the graphics editor, except this time, use GFX, Scenery, Export, DO NOT mess with the CRE. 
-To work with these, open TLP, click open, it will only show .smc and other video game ROM files under the default settings, if you open your SM ROM you can make other edits that I will get to later in this guide. As for NOW, you're going to want to set "Files of Type:" to "All Files" Notice it will also say, SNES, and then rom extensions, NES, rom extensions, etc. These are irrelivant to this guide, if you were working with M1, Fuison, or ZM, these would be slightly more relevant, for the aspect of editing the ROM, note those games also use TLP functions, so if you convert your hacking expertise to another game, your TLP knowledge goes with it. 
-Now that you have your parameters set properly, you're going to want to open your file you ripped from SMILE, it should say "*Name of SM ROM file* *Grapics Set Number*.gfx" Open this file. 
-Now you notice a jumbled mess, don't freak out yet kids, the ride just started. If you're an astute user, you'll notice that the "File" and "Help" turned into a bunch of new options like "Edit" "View" "Palette" and "Window" These are very important. Now, click under palette, load, and then "*Name of SM ROM File* *Graphics Set Number*.tpl" Don't mix up your GFX file and your TPL file. The nice thing about load palette is that it loads just TPL files, so no parameter changing, however, if you screwed up and loaded the TPL file on the last step, YOU SHALL NOT PASS, and return to the prevous step to get the right file loaded. Now you're statement is gonna be "What the fuck Japan Tobi, your a cheap, this is just a bunch of random crap!" Yes, exactly! Now, an astute person will ALSO notice there's only 2 colors in each palette, in a 16 bit game (16 bits, 16 colors per palette, minus one for your transparency color, but I'll cover that later) This is because we're view mode for 1BPP, in other words, some basic programming crap SMILE understands. If you try editing this you're gonna get a mess. There's an easy fix, however. All you have to do it go under View, Format, SNES. Notice here there is ones for NES, GBA, etc, you don't need those for SM, they'd also screw you out of 8 colors (NES being 8 bit uses 8 colors minus one for transparency, not that this would break your game, but it would limit your capabilities, and in conversion it might screw stuff up, I'm not really sure because why would I do something the way I know is wrong) 
-Now if you did everything above successfully, you should have something that looks like the Graphics Edior in SMILE, congratulations, you have been promoted from n00b to Semi n00b! If not, try again >:U
-Now you will see the very first color looks kind of funky, there is an explanation for this, read carefully because this will keep you from screwing your ROM up pretty bad
--There are 8 (0-7) palettes in a TPL palette, at least, 8 ripped from game. I will explain below in depth on what each one is and how the operate. Palette names marked with an "[X]" in front of them are palettes you shouldn't touch yet. 
[X]PALETTE 0: CRE. This contains colors for the power bomb door, Chozo Statue, and a bunch of that junk, messing with this palette is a bad idea.
[X]PALETTE 1: CRE. This is like the first one with the colors for the super missile door and all that junk, again, don't touch this
[X]PALETTE 2: CRE. Same as first two, but with missile doors. Don't touch
[X]PALETTE 3: CRE. Before you bite my head off, this is the last CRE one, this is your general Blue Door colors. 
PALETTE 4-7: These are for your actual use. The first color in each one is a transparency, in other words, when you use this color, it shows whatever the background in the room is. The other 15 colors are yours to choose from. BE sure not to create a 9th palette, you'll overwrite palette data and completely fuck your entire ROM!! If it's solid black and you still need more space you're out of luck, you may be able to repoint data, however, SMILE itself only handles 0-7 so repointing is more only for actual space, and besides that, repointing is a guide all its own, as well as being something way out of the league of users this guide is designated for. 
-Getting palette colors
As I'm sure you've realized, barely any graphics are in TPL formal, there's a solution to this! If you open a PNG image you'd like to use (PNG ONLY! JPG, JPEG, and a lot of GIF files are compressed and it adds more colors with less definiton, and when you're limited to 15 colors, you need to conserve like hell!) in GIMP 2.9 (Recommended) or your graphics protocol of choice. If you find your color selection tool, in GIMP it's the little eye dropper, and collect your first color, you can open this color on your editor. In GIMP it's the foreground color, all you have to do is click on this. A menu will now pop up with a bunch of letters and numbers, if the color is a generic black it will read like this:
H: 0
S: 0
V: 0
R: 0
G: 0
B: 0
Anybody who knows general physics knows black is the absense of all colors, hence zero. This is also expressed as #000000 in HTML, but we're hacking not web desiging so that notation is dead to us at the moment. (NOTE: Not all the HSVRGB numbers convert to the HTML, for example, this shade of red I randomly used for this is HSVRGB of 0, 100, 69, 176, 0, 0, and its HTML is #b00000, unpertinent information, but I like to clarify) Now if you click your first color, your transparency, set a color you can look at without confusing yourself. I usually choose a Blue Screen of Death type blue, black especially makes for a bad transparency with darker tilesets, same with white in lighter, just figure out what works for you. Now on your SECOND color, You will see 6 numbers marked "Hue: Sat: Lum: Red: Green: Blue" This is the same as Hue, Saturation, Volume (Or in an older program like TLP, Luminosity), Red Green Blue, or as you'll see me use for short, HSVRGB. These numbers can be copied from GIMP to TPL, just correspond the numbers, for the dummies out there, if there's a 0 in Hue on GIMP, type 0 in on Hue in TLP. Always remember they go in the same descening order, and don't get confused over the difference between Luminosity and Volume, remember they're the same number, it's like Americans saying "garbage" and Britans saying "Rubbish" Do that with all needed colors and congrats, you just converted some random tiles you found on the internet to Super Metroid! This is especilally helpful when ripping sprites from Game Maker tile sheets like AM2R, and a lot of the ones found on Metroid:Fan Mission, great tilesets, just need to be ripped over. If it's another ROM directly you wish to rip from, there's separate tutorials written on that, again, a little but more advanced then this guide. 
-So now you're saying "Well I got my colors, now what about my graphics!" Now there's the easy way, and the hard way, or as I call it, the advanced way, and the n00bs way. 
n00b Way: Set up gridlines of 8 pixels by 8 pixels on GIMP and draw in what you see in each one, 2x2 of these 8x8 boxes makes a tile in SMILE, which will be covered further down. 
Advanced way: Look on "Converting Photoshop to TPL" by Red Monkey, this is in Metroid Construction's trading board. NOTE that this methood is less n00b friendly and geared towards photoshop and not GIMP, so have fun. 
-So I got what I want, now how do I get it back into SM??? Simple, remember how you exported your graphics and palette? There's an import button right below export. Click that and you will be prompted for the files for each one the same way you were prompted by Tile Layer Pro. Now this will probably jumble the graphics set you were working on, to save this, click palette, save. If a warning comes up saying you're over the data limit, don't save it. You either made a 9th palette which I warned about above, or you just used up too much space. Solutions for the palette problem, erase your palettes over number 7. Solutions for the graphics problem, either import to an area like Norfair that accepts more data from GFX sheets, which is the easier way, or if it's that great or you have your heart set on that location, repoint. There's plenty of guides on repointing on Metroid Construction, but they're a bit beyond the basics, and some are less user friendly or less detailed. 
-Getting your grapics on a sheet is a bit different, remember how I said 2x2 of 8x8 squares makes up a tile? This is where that comes into place. First, click on a tile on the sheet you want to change. It will display this tile, which is probably jumbled now, it will have a bunch of rectangles around it with numbers in the corner. These numbers represent what palette (0-7) you're using for that tile. In other words, if you drew your tiles on palette 6, you'd click 6 in all 4 corners for all your colors to look right. The rectangles are arrows that can flip your tiles around and such, but since you just left TLP, I'm assuming you would have already flipped things around and all that crap. If they're already clicked, unclick them so they don't mess up your tiles. Drag over each 8x8 tile, when complete, there should be 4 pieces in a square that make up a tile you made, if it looks correct, click "Save 16x16 tile to ROM" and go to the next one until your sheet is finished! Your transparency also comes in play here, if you're using a layer 2 or any colored background, make sure your transparency is on any space outside your tile, in other words, if you have part of a rocky floor and there's space above the top of your floor, color those spots in with transparency so you don't get a black background over your background. When you're all done, click palette, save, and enjoy level design!
--CRE EDITING--
-Not going too in-depth on this because for one, you're probably not going to mess with it too much, and for two, besides the few rules, it's simple as all hell, at least the same as the other editing.
-With CRE, you have to understand that you affect the colors of your doors, for one, as well as some animations like item pickups, shot blocks, eye doors, etc. the CRE is more for decoration in your tilemap, however, it's very important to your PLM's. Those who want custom PLM's, the CRE is what you're going to mess with. Also note CRE is in all tilesets, so if you change something in one, you gotta change it in all, otherwise your CRE will be different in other tilesets as far as changing palettes, changing GFX carries over to every set. In this note, to rip CRE graphics, you just have to go "GFX-CRE-Export" Your CRE colors are in your set's palettes 0-3, as explained before. If you say make the yellow bomb doors green in set 1, it will stay green in set 1, but be yellow in all other sets. If you redraw an energy tank in set 1, it will be the same drawing in all tilesets, got that? You should also be aware that if you per say, set colors up for new CRE in palette 7 of set 7 (Like I did in my hack) You're obligated to set palette 7 to those colors in all sets to make sure it stays correct, this is because you have to click the numbers to set 7, and they read off set 7 then on, this is done more when you group a lot of things together, IE making energy tank, missile tank, super missile tank, and power bomb tank all in one palette but you don't want to fuck up your doors, or worse, your animations. Other than that, CRE is about the same as any other set, the odds of you dinking around with it are low, and if you do, it's minimal for things you want to use all over, and usually you're just revamping or converting to other games or personal themes. 
--START UP EDITING--
The only one you're probably going to edit is Title 2, in other words, the Super Metroid Logo with the Nintendo thing. You can easily rip this at the bottom of the Graphics Editor by selecting "Title 2" and "RIP" you can use this to change the Nintendo logo (LIke in mine it now displays The Doors logo) or the title screen, it's not necessary and a lot of hackers don't do it, but if you're serious about your hack, it's nice to know how to acquire the palette and set. To import it again just select "SAVE" under "Title 2" it will bring up a browse window, click the set you worked on, then it will close and have automatically saved. Run QuickMet to see any Nintendo logo changes immediately, run the actual rom in your emulator to see the title screen changes. 
--SPRITE EDITING--
In this end part of the guide, I will teach some palette editing, PALETTE, not graphics. Palettes here are one thing, graphics are on a whole other league. To edit enemy sprites, certain Samus sprites (Like the ones on the pause screen) etc, are edited in the actual SMC, I said I'd touch upon this earlier. I'm only going to discuss the tip of the iceberg here, which is editing enemies, particualarly, their palettes. The palettes can be acquired in SMILE. Find your enemy, in the DNA section, use the scroll bar to find the "Enemy Palette" it will have some 4 character thing like E47F or something, when you click the button, it brings up a small palette with buttons saying "Rip Palette" and "Import Palette" and "Save Palette", rip it, this will say "Ripped to "E47F.tpl" or whatever enemy code it is. Now in Tile Layer Pro, when it automatically searches for .smc files, click your hack. This opens up a bunch of jibberish, it's already set to SNES view mode (Because it's an SNES ROM and already recognized as SNES format) Load your enemy palette under the palettes window like you would with CRE or Scenery. If you scroll through until you find the enemy you're looking to edit, you can play around with their colors and such like any other edit, when you're happy with your changes, save the palette, re improt it through prevous steps, and enjoy your recolor. There may or may not be guides on creating new enemies, or changing existing graphics, I know there's ones about cloning and such, but I barely understand them myself and I feel it's both beyond this guide, and it's beyond my expertise. Note that there's tons of other edits that can be made in non enemy stuff here too like the pause screen, item names in the collection popup, etc, but to discuss those would get lengthy and it goes a bit further into things then I wish to, I may submit another guide on that depening on how I feel. This about concludes basic GFX editing, and I do mean BASIC. If this helped you in any way give me a shout out, make any graphics thanks to me I'd love to see them, I'm always hanging around Metroid Construction if you have any questions on this or more advanced stuff even shoot me a PM, I don't bite, at least not too hard :P I wish all of you the best of luck, see you next mission!
-Japan Tobi
TobiMikami