Frankly, this game's getting a little stale once you've seen it all and done that. Here's yet another place we can spout ideas for stuff like this.
My personal favorite is the Space Biome. Basically it'd either be set inbetween a series of "asteroids" (basically sections of land, these vary in composition, say one is limestone and another just plain stone.) or larger bodies, say moons. Pick your poison. But beware. You'll see quite a few more brains than you're used to (sorry, no evokers!) and you'll have to worry more about your oxygen running low. However a rebreather would serve to mitigate this risk. Otherwise another consumable (oxygen tanks) could be used. Neglect to do both and you'll slowly asphyxiate. Dungeons would also be somewhat more prevalent in these biomes, and somewhat less dilapidated.
Best of all? It means I don't have to wallpaper my worlds in space backdrop anymore whenever I want a space themed world!
Anyways, discuss whatever ideas you have. Go crazy. (Totally not redundant)