The atmosphere and terrain are really well done and faithful to the original, but I can't help but feel it's missing something. I think it's really hard to tell what exactly is going on with this planet just from the scene... somehow it always struck me as a frozen planet with an atmosphere, but that could be subjective.
At any rate my suggestion would be to add a little extra variation to it, this could either be from some clouds (not too much since I don't think you want to hide too much of that nice surface), or just some small brightness/contrast differences directly to the surface to give it a bit more flavor.