20 Gal tank, looking for company!?

I'm looking into getting a few more fish for my 20 gal aquarium. I have 1 betta in there right now with 4 dwarf frogs, and 7 neon tetra's. They all get along great! What do you think would go along nice. I can't have anything with a big showy tail, as my betta wouldn't like that, and would probably try to kill it. I don't really want any guppies or platy's, I've had them in the past.