Welcome to the site, by the way, Cheetahkita!
I would agree with Omorrokh, a female betta (which can be just as beautiful as the males) or an African Dwarf Frog, or one of each.
Some of the colorful small shrimp would be pretty with some live plants in there... cherry shrimp or some of the cardinia species (we have a lime-green colored small shrimp that is real cute.)
Or you could save up your money and buy a 30g tall tank and get a pair of angelfish with some bottom feeders or something and have a betta in the small tank.

(Induced Multiple Tank Syndrome at its best)
