Day geckos do well in there. Lagodactylus williamsi is a striking bright blue small day gecko (the males, anyway). I have found that gargoyle geckos don't seem to be as active as crested geckos, so I'd consider that size for a single gargoyle. You could also put mourning geckos in there. They are parthogenetic so you will have a lot of them eventually. If you do put small day geckos or mourning geckos in there, you will have to narrow the crack between the front door and the glass sides by building it out with clear packing tape (and be sure the sliders at the top back are closed).

Aliza