In my 55g I have;
18 marbled hatchets (the marbleds are hardier than the silvers, IME)
42 false neons
12 glass catfish (they're quite delicate though, and not colourful, so you'd probably want to skip those!)
2 BNs
a royal whiptail catfish
You could swap the false neons for whatever tetra you like best, or even split that number into two shoals if you wanted to (although I think larger shoals of one species looks better). If you have a sand substate you could have some corydoras instead of the glass cats; 6 or 8 would be a good number, as cories are chunkier and produce more waster per fish than the glass cats.
I do have a massive external filter, do 50/60% water changes weekly and built up the stock very gradually over a couple of years though, so you might need to adjust the numbers down slightly for your system.