NA is often a problem because of water temperature issues (you'd need a chiller), and fish size issues. It'd be great if you could find *southern* North American fish that enjoy higher temps and don't get too large. Jordanella floridae (American Flag Fish) is one I can think of. Also, Procambarus clarkii, blue cayfish, are from the south, and are tolerant of all temperatures.
The Mongabay website is a great one. Check out their many, many great ideas.
I'm always reluctant to do a full biotope, as it's tough to find an algae eater native to a region, and it's often tougher to get all the fish you want from local dealers. You have my vote for an Australian River or New Guinea biotope. I love rainbowfish (well, not all of them; some are kinda boring...).