Here are a couple of our smaller tanks.
The first is a 5 gallon tank that my son has done. It currently has some Barbs, a few blue velvet shrimp, & snails. We had some neons, but they have recently left for the other side. He is just 8, so I think it has been a fun tank for him to get started with.
Next is a 13(?) gallon cylinder tank. It has some Danios, Rasboras, Hillstream Loaches, snails, and a bunch of Firered Cherry shrimp. It is still a pretty young tank, so I am still trying to get the plant the way I would like them. I really like this tank, but I don't think I will ever do a cylinder tank like this again.