Small schools of fish, at least for me, look quite naff, so rather than have 6 of each of something x 2, pick one single species and have 12 of them.
There is no reason why a tank this size cant look good, but start stuffing it full of lots of different fish it will just look naff.
You mentioned neons and there is no reason why you cant have 12-15 of them, that sort of number will make an eye catching display, especially if you decorate the tank nicely, with a dark background to bring out their colours.
With this number of neons you can still look at half a dozen corys, but again, you want 6 of the same type. Check out whats for sale in your local shop. The smaller species of Cory would be better, if you can find Panda Corys (very common at the moment) you could probably home about 8 of them. These guys need sand as a substrate, not gravel, thats a rule pretty much written in stone for cory lovers on here. Play sand from Argos is good enough, (washed out well in a bucket) with a few bits of wood to hide under and if you can use a hacksaw, pickup a few coconuts from tescos and chop them in half, they make perfect little caves.
If you like Gouramis, you could look at
Dwarf Gourami a pair would do nicely as your center fish.
With this stocking, you would be pretty much maxed out and all you could really add to complement the tank would be an Apple snail or two, which are freakishly quite interesting to watch.