Checkerboard barbs would work very nicely. A school of 6 or 7 would fit in with no problem. They are a schooling fish that stay small and are very active. They don't bother any other fish.
I have a small school. I find them great fish.
The gold barbs would work but they can get big due to the fact that they are gultons. You would have to limit yourself to 3 or 4 of them. Same would also go with rosey barbs.
Their big downside is making sure that the other fish get food with gold and rosies around. They tend to pick off all the food before the other fish have a chance to eat.
The cherry barbs are really excellent little community fish. They get along with other fish, the males are beautiful and there is the added advantage that they eat algae.