Hi there....I can't think of any desert lizards that are tree-dwelling. Most of them are ground/rock/crag dwellers. I think the collard lizards and spiny swifts are some of the nicest. They are more in the 14 - 16" range. The smaller ones would be side blotched lizards, some small geckos [ moorish, fan footed, white spotted ] those are just a few off the top of my head.