I'd say cardinal tetras, corydoras, and hatchets... You should be able to get a good school of each in there (about 12 cardinals, 6 corys, and 8 hatchets, and you'd have action all over the tank. Dwarf Gouramis look really great, but most of them carry some parasite or disease (I don't remember which it is) and don't live for very long. You might have to go through a few before you find a healthy one. Silver Dollars would just nip fins in there -- not really enough room for them, and they're pretty bad fin nippers.