I've been feeling like the levels in Nova the Squirrel 2 could look better, even though people tell me they look just fine. So I've been looking at different SNES and Genesis platformer games to see some good examples of how other games decorated their levels. I thought it'd be interesting to share my notes and thoughts here.
I initially looked at some GBA and DS games too, but the ones I looked at (like Kirby: Nightmare in Dreamland) seemed to go for an art style that just looks like a really good (but also very complicated) illustration instead of something that's built from trying to reuse tiles. It felt like an unrealistic expectation to be able to match something like that as someone who doesn't have experience drawing anything like that, and there would likely be issues with fitting the art into video RAM if I did, so I decided to just stick to SNES and Genesis.
Super Mario World is much plainer than I remembered, but still looks cohesive and makes it work anyway. It's a good example of how a game doesn't need to have extremely complicated art to look good or be loved. It gave me a lot of confidence that I'd be able to make something good that I'm happy with.
Adding little non-solid decorations like bushes, flowers and fences to Nova the Squirrel 1 for NES made it look a lot better (and made the world look like it was more alive), so that led me to think that it was really important to have a lot of variety in these kinds of decorations to keep levels from looking boring. But that wasn't the case at all when I looked at licensed SNES and Genesis games. A lot of them have a small amount of variety, put the decorations into the terrain itself, make the decorations really minor and unobtrusive, keep the decorative parts mostly restricted to the background layer, or some combination of those. And they still look pretty good.
I noticed that a lot of games try and make the foreground you actually walk on more interesting, with a variety of different materials and just making the terrain itself look really elaborate. Mega Man X has a lot of mechanical looking terrain (and some snowy areas that have things sticking out of the snow here and there), and Yoshi's Island puts lots of flowers and other plants inside the terrain itself, alongside things like large rocks being built into the level shape. Kirby's Dream Land 3 has its own take on having very interesting terrain, with patches of dirt and grass alongside things like flowers inside the terrain, and it'll even often have little holes in the terrain just to make it more interesting.
And some games that put a lot of focus into making the stuff you walk on interesting don't really even bother to put distinct non-solid decorations on top of them, because the level is already decorated enough.
For games that do put distinct decorations on top of terrain, a lot of them will just use a small number of decorations and continually use them throughout a level, or throughout a whole game! Super Mario World seemed like an extreme case here where it mostly had a little bush and a much larger bush and there wasn't much else. It looks like it's actually perfectly normal to reuse the same decorations over and over, and it probably honestly does a much better job at establishing a theme than having too big of a variety.
Something I want to point out specifically when it comes to foreground decorations is that Yoshi's Island and Kirby's Dream Land 3 both do a lot of stuff where they'll put some sort of nonsolid "wall" behind the player as a form of decoration, to imply you're in a cave or tunnel or other structure. And then it'll do something interesting with the shape of that wall, and put holes in it here and there. I suppose Super Mario Bros 1 has a very early form of this.
Here's some platformer games that had backgrounds that I thought were probably helpful to try and learn from. They may be simple in design, use few colors, or seem to be prominently built out of repeated elements:
Aero the Acro-Bat has some good examples of using silhouettes effectively, which make for easier-to-draw backgrounds. Some backgrounds have multiple levels of silhouette too; there's one that has mountains and then on top of that there's Ferris wheels and other structures. It also has some backgrounds that are just kind of abstract and have repeating patterns, yet still look good and work fine.
Kirby's Dream Land 3 especially is worth pointing out because it has some extremely simple backgrounds (take this one for example) and yet it looks great. That makes me think that maybe sometimes the important role of a background is to contribute more colors to the overall scene, and lead you to a balance of colors throughout the level that looks good.
I noticed that if you're looking for simpler backgrounds with fewer colors they're probably more common on Genesis than on SNES, probably due to the fewer amounts of colors it can use overall. But, it doesn't look out of place when you do that sort of thing on SNES.
Sometimes games will make their backgrounds look like level layouts themselves, with terrain that just happens to be behind the player. Some parts of Mr Nutz do this. This might make it easier to make backgrounds, because you can build them as if you're building a little level?