Apistogramma cacatuoides !!!! and some rams. lots of neons ofcourse. killie fish, gudgeons, pacific blue eyes, celebs rainbow. loads to think of. your going to have a tough time selecting lol
You could get a school of 40-50 tiger barbs plus some bottom feeders - that would look sweet. You would be more limited on what you could put in with them though. Very active, however.