You'll get a lot of dfferent ideas. I've never been a big fan of Red-tailed sharks because they can become fairly aggressive to other fish.
You could go for a community tank which would include a lot of fish such as angelfish, the zebra pleco, cory's, tetras, gouramis,.... There are endless possibilities.
So select 1 specie of fish you would absolutely love to keep, then build around it.
Hope this helps!