Like someone mentioned before, why not realistic sceneries? My first project is a small town in Germany, framework, a small railway station sourrounded by houses built in the 19th century, rural environment around, nothing spectacular...
Here is a picture:
I am still at the beginning, no details but this world will be full playable.
This is probably suggested, but how about these:
A town that was exploded somehow, and is now completely in ruins.
An alien planet(All neon and weird?)
Ocean with floating islands that contain the lots.(One island holding residential lots, one with shops, one with careers) Transportation: Boats