If you want a small enclosure and something nice to look at, I'd look into the bolder varieties of Dart Frogs, Tree Frogs, or Bumblebee Toads. They're charming, and some can be housed in something like an 18x18x18 enclosure in pairs or small groups.

I have both a Green Tree Python and a male Jungle Carpet Python, adore them, and could look at them all day - but it sounds like you are maybe looking for something that needs less space, so I thought I'd mention these guys since they can really be delightful as display animals.