If you want a theme that is unique, you'll have to come up with yourself. Some more unique ideas would be themes that are related to interests you have but not a lot of people do, for example, you could do something like the Disney and Anime towns but make it about other TV shows, movies, or books you like.
A good way to start thinking of a theme is to ask yourself which villagers you like or at least can tolerate. You won't want to end up with a theme that would make you have villagers you hate (if you want themed villagers). Are you going to make your own patterns? Because if not, knowing what kinds of qrs are out there might help you think of a theme as well.