Are you looking for something easy but attractive or something more challenging?
I'd say a school of black phantom tetras (5-6 of them - males will display beautifuly), 2-3 otos (attractive and will eat algae) OR 4 bronze cories (wonderful characters) and a trio of honey gouramies (not as fragile as dwarfs but just as beautiful and a similar size - a male and 2 females would be best) for a realtively easy but beautiful tank to maintain. I'd have a sand substrate or very fine, smooth gravel becase the cories like it (if you go for them instead of otos) and some floating plants for the gouramies and some rooted ones to add some interest for the tetras.
Alternatively, a well-plated tank, with sand again, and a shoal of say 7 cardinal tetras and 1 or 2 dwarf gouramies and 2-3 khulie loaches. This might be a little more challenging because of the fragile nature of cardinals (though they aren't as bad as neons) and the mass-produced and inbred but wonderful and colorful dwarf gouramies. Not difficult though.
If you are prepaired to go for a species tank, killifish are colorful and interesting but I would reccomend some floating plants for this setup. The substrate doesn't realy matter but sand looks nice - or very fine gravel. Another option for a species tank are dwarf puffers. Or you could go with a heavily planted tank with a huge shoal of harlequin rasboras or cardinal tetras or golden dwarf barbs or black phantom tetras would also look beautiful.
There are endless options - it depends on your own prefferences.