So far, I've done a prison, a campground, trailer park, a homeless family. The prison: Each cellblock is 2x6 and contains bunk, toilet and sink, nothing else. They've got their basic areas - a kitchen, dining room, library, work-out room and an exercise yard, but no outside doors. Campground: I make a buncha one-room log cabins along the perimeter, with the main one by the road being a dining hall/"camp store", and some "outhouse facilities". Usually a pond somewhere, and usually a swimming pool/playground directly in the center. Homeless: I design the residential lot to look like an abandoned city park, and saw on someone else's site how they built a "house" to look like a cardboard box. Oh, and I've done an apartment building that looks like a city housing project.
Let's see, what else... I've done the Suleman family (boring/annoying, to me anyway), I've tried Harry Potter, a couple other ideas like that.