The fish already mentioned would work well with the tetras. Just watch angelfish and bettas though as they can be aggressive. I had a betta in my tank and he would kill any fish that were about an inch, inch and a half long and he injured my striped zebra fish pretty badly.

Check out mollies. I really enjoyed having mollies because they were very active fish that would actually interact with me. They always got excited when they saw me come in the room and they would follow my finger if I slid it across the glass. They are live bearers though, so be careful about what sex they are. Males will fight and if you have a male with females, you will probably end up with babies. If you aren't prepared and have the female in a breeder, then the babies will just get eaten by the other fish (which is completely fine as long as you don't mind it).

Striped zebra fish were cool, platys, glass fish....