Something about the color scheme of your tilesets reminds me of Batman: The Animated Series. I think it's the dark backgrounds.
The Metroid Engine is set this way, that you ONLY have a foreground layer, means 'air'/passable tiles are always in front of the sprites. That's one real knockback one has to deal with when hacking this game.
This means having black, much black, i try to compensate it with many detail tiles. It's a real task for the landscape not seeming bland and boring, but lively, vivid and exciting.
I liked Batman the animated series as a kid, so i take it as a compliment