I've been wanting to have my SNES game deliberately do uncommon graphical stuff during levels (or at least uncommon for platformers), though for some features I have ended up realizing that they're probably uncommon because in practice it's tricky to do something worthwhile with them in this context. Though that just kind of make me want to make it work even more.

I feel like 256-color modes are really cool, but mostly shine for helping you show graphics that aren't aligned to a 8x8 tile grid, like Sim City 2000 or Bust-A-Move or Zoop. When things are on a grid it's tricky to find a situation where you genuinely benefit from >15 colors in a 8x8 space. Some especially smooth gradients maybe??

I wanted to do some silly stuff with using the high resolution modes to display the level with all of the usual art, but zoomed out. It looked pretty bad because doubling the vertical resolution means interlacing, and interlacing means you get some really awful flashing unless the contrast between scanlines is low. I do think that increasing the resolution would have more of an obvious visual change than just squeezing a few more colors in per tile, though I'd prefer to do it without interlacing and the resulting 512x224 sure is an awkward resolution. On the other hand if I deliberately want to do something weird then awkward may in fact be good.

My engine does support some weird stuff that's just using the commonly used stuff but in a silly way. It can draw levels with sprites instead of background tile, which seems most useful to have a regular looking level that happens to have mode 7 in the background (which has looked really cool when I've seen other people do it). Alternatively I can have four levels of parallax in the background.

I'm also playing with doing stuff where I have a 15-color layer, 3-color layer, and 15-color layer in that order, instead of the 3-color layer being another level of parallax or a HUD like it usually is. I like the idea of using a 4-color layer to add some extra detail, like a wall behind some foreground elements.