Last I knew, modern and medieval themes sold well - and look nice; very big or very small buildings, usually. A few months ago people also liked the idea of hobbit holes and underground living, or living up in the sky. Usually underground or in the sky looks pretty neat, too, and is fun to build (although very time-consuming).

It really depends on what you like, what you are willing to build, and if the town would be a project or profit. If you are looking for money, you may consider making the town a farm (partially or entirely). However, if you are looking for a nice project, you might find ideas in the Towns and Nations forum threads. Often I browse there and Google to try and come up with something different.

 

NOT. A. FLAT. PROFIT. TOWN.

Make it creative... Don't go along with the trend of flattening your town and selling as many plots as possible - make it look nice!!

 

I would really like to see a nice mountain town, that I would buy a town in. You could just build a large farm and sell perms to it.

 

I disagree with this as, if you ever decide you want to sell your town, flat towns sell for more. Make it creative