I love the tank, what kind of filtration do you use?
I think some sunfish would be awesome. I would go with less common sunnies like Warmouth, P-Seed, Shadow Bass. Also, Crappie would be really cool. A small school of minnows would be nice too. The larger ones, like mentioned Golden Shiner, or some Shad can get big.
Hey Josh; I have a 80gal sump with 3- 2000gal pumps pushing it.