Rebuild and remake the whole town challenge?

One thing I am not sure of yet is how to decide which themes to use for each world or even neighbourhood. I would like to save the world in a blank format before I start building, so I can use it in the future, but I definitely need something to aim for. I definitely want to place more shops as I so rarely use that aspect of gameplay, so I think it would be fun to experiment with that, and perhaps make one of the smaller neighbourhoods a shopping district.

The other thing I'm not sure of is what to do with the apartments, because there's a limit to what I can do with those.