I love the look of whitewalls on certain bikes. Mine included. However the ones I like are on Old School Bobbers, and Various Baggers. Of course it also depends on the Wheels of choice, the fenders of choice, and the colors of the bike. For instance, a bike with a 16 or 18 inch rear and 21+ inch front, kind of looks goofy with white walls. However a pair of matching 16/18's make a decent mount for white walls. The bike you bought... In my opinion, wouldn't make a very good place to use white walls. definately stay black. If down the road you decide to change up your fenders to a more of an FL style, it may look half way decent with a pair of whites on it.
I was in your same predicament recently. My one buddy got a new Fat bob and the front tire was a nice fatty. I told him how much I liked my white walls and he went out and bought some. When I saw his bike.... I wasn't very impressed. He didn't talk to me half the summer till I offered to change the tires myself.
I also saw a guy this spring put a pair of white walls on a new Cross Bones Springer. Man was that UGLY!