I have a weird feeling that we're going in a wrong direction. I think I'll just return to making this tileset when you'll be sure which tiles will you use. Just remember what's the theme, because right now only n0's tiles and the door remind me space, and only Violet's tiles remind me a temple, while the most important tiles of the tileset (the ground) remind me that cool game Knytt Stories, which has nothing to do with space nor a temple.

About the cave tiles, I think they're too bright. Maybe it's just me, but before I read they're for cave, I thought they're solid. And we already have something like cave tiles, but I guess I'm worrying too much.