Angelfish would be wonderful in this set up because it is deep enough for them. If you get angels, I would get a single one so you don't have to worry about aggression between other angels if they don't pair or aggression towards other fish if they do pair. An Amazon setup would be fantastic to watch.
Balas need a six foot tank, I believe. This tank is not long enough for them.
I would do something like this:
1x Angelfish
12-20x corydoras of your choice
3 bristlenose plecs
20x hatchetfish (be sure you've got a secure lid)
Angels eat neons, so you would need to avoid those. You could probably do more fish in the schools, but I would comfortably do something like that. You'd need sand, too.
Hatchetfish would be cool because they are interesting looking and are not small enough to keep in a small tank. They are also pretty active, I hear.