Cresties are nice, in a viv that size you could have a male and a couple of females, or three females if you don't want eggs
They can live at room temps. so heating is easy, and as they are from a tropical island, you can have a very attractive viv.
This is my viv, it is 24"x12"x24";
These animals are easy to handle, and great to watch when they hunt, just don't get your finger in the way