The clouds are good. You may want that big patch of over-exposure in the sky to give the feeling of desert heat, but if not, saving as OpenEXR and playing with combining exposures could help - or if you don't have the tools for that, doing a couple of renders at different exposures. Like TheBlackHole says, you may want to alter the max slope limit. Also, the jaggedness of the landscape doesn't look so good in the far distance
