I have a school of gold long finned danios with my tigers. I plan on keeping the tiger to about 8 and upping the danios to 10 or 12 (55g tank). They are good together because the danios are so much faster than the tigers. I have to watch the feeding on bloodworms days just to make sure the danios get enough, but I think they are a good match. It's a nice contrast.
Whatever you pick just make sure they are quick and pref in a school.