I can't remember if I'd heard this suggestion before or if I'd thought of it myself, but this was precisely what I entered this thread wanting. I'd love to try my hand at making this myself, but it would probably end up one third finished and I'd be dissatisfied and never touch it again.

In the 'show some levels...' thread I presented a tileset I started making but haven't touched since, but Mike gave me some good suggestions that it could eventually feature a ruined civilisation overrun with nature. I think that might satisfy a handful of the other requests I've read, but I quickly ran out of ideas in making the mechanics of it.