My theme is 'tropical (fruit trees) in ths south, yet forest-y in the north (cedar trees) and with a bit of nostalgia-based ideas and things I like'.
I do kind of have a theme for certain areas, for example I want the area around my campsite to resemble a French camping - based on my own experiences with camping in France. I'm also planning to have some Dutch pride in my town with a windmill surrounded by a tulip field, and a scarecrow somewhere in it. Like I said, I want to give the south of my town a tropical feel and the north of my town will be more of a pine forest. I'm sure all this isn't the kind of theme you meant though, so I voted 'nope'. :)