Hi, I wrote
this post on NES restrictions. That covers how it's all handled, but I still feel it's a bit too specific if all you want to do is make art. Anyway, still worth a read if you haven't found it already. If there's anything you need broken down further, ask a specific question.
Are you looking to just make a mockup/graphics, or an actual game? There is a lot more stuff you have to decide and know if you want to make a PC/whatever game that's accurate to NES.
I was under the impression that each tile must be 8x8. How many 8x8 tiles should I make per BG? I know it slightly depends on what the BG must look like, but I've seen some pretty complex ones on here that I didn't thought fit within the rules of an NES game.
Yes, 8x8 background tiles. You are (generally) limited to 256 unique background tiles in whatever you would consider a level or map for your game. I can say that if people who pretty much know what they're doing are going to break a limitation, it's usually the 256 tile limit, heh. But you might also be surprised at how clever people get with tile use.
This is a fun post. It's not about an NES game, but it does cover some masterful tile work.
4 background palettes of 3 colors, plus one color you can use anywhere. Think of it like this: The background is filled with the one color. The 3 colors from a palette can be used to draw on top of that color. If nothing is drawn on top of the one color, it's still there. These palettes can be changed during gameplay (it's how Mario ? blocks flash), just know that everything that uses that palette will be changed when you change a color.
Each 16x16 area can (generally) be covered with the 3 colors from any 1 of the 4 background palettes. (This is another commonly broken one. People tend to use a palette per 8x8 area, not 16x16. But technically this limitation can be overcome which is what the generally is for. )
8x8 sprite tiles. You are (generally) limited to 256 unique sprite tiles in whatever you would consider a level or map for your game.
4 sprite palettes of 3 colors + transparent. These palettes can be changed during gameplay, and everything that uses them will be changed like with the background palettes.
64 sprites on screen at once.
NES sprites are 8x8, or 8x16. I'm just going to assume you're using 8x8 sprites. The way 8x16 mode works is weird to plan around if you're making graphics and wouldn't save you many sprites if you plan to have 16x8 enemies, anyway.
Any advice would help, but I would REALLY appreciate the info regarding complex BG with NES limitations so I can hop to work.
You need to be more specific than this. NES limitations are much less rigid than you'd think, it varies depending on the board the game is run on. So name some games that do the things you'd like, or just state the complex things you might like to do for the background and I can tell you if it's possible and how it'd be accomplished.
Quick critique on art: You have outlines on the rotating asset, but not the enemies which is a bit inconsistent. If this is intentional to make the bullets and things to dodge stand out, it may be okay. But if it wasn't a conscious choice, go with one or the other for everything. The three things you have use three different palettes. This means you have only one left. If you plan to use yet another for your main character/ship, that's all 4. Depending on how you want your game to work, you might only get four palettes for each zone of the schmup, so if you want lots of different kind of enemies, the palettes need to be as reusable as possible.
If it's the kind of schmup that you're over black space most of the time, it may not be worth it to have black in your enemy palettes. You can just draw things within the sprite that you want black transparent.
