Very Biased but I would go the threadfin rainbows too, they are a stunning fish, if all but impossible to take a good photo of. I just did a major water change on my threadfin rainbow tank and now the males are all displaying and showing off.
Some suitable co-inhabitants with the threadfins would be delicate blue eyes, or spotted blue eyes which are also small and pretty.
Khuli loaches would also work well with these guys (although mine live with a pack of corydoras) and shrimp would also stand a chance of surviving with the threadfins.