If you want to propose a change to an existing structure (like villages), or add something brand new in a current dimension or biome, this is the place.
Caves Update under review
Crystal Caves under review
Plains structure (was: More biome structure) needs info
Lakes under review
Abandoned Castles in Snow Biomes/Mountains under review
The Beaver Dam, The Beaver, Stick Block under review
Naturally generated structures need redesign under review