I'd do a couple of small schools (8 or so of each)... maybe harlequin rasboras and rummy-nose tetras. Then a group of panda cory cats (6), and maybe one centerpiece like an angel or pearl gourami. That would be a beautiful tank.
But, that's just my humble opinion!
Or you could do a semi-aggressive tank. Fill it with different colored tiger barbs, then add a red-tail shark. Maybe some serpae tetras.
What else you could add to that, I'm not sure. But I know that would look cool, too.