Astr0s. Thanks mate. Yeah i've been thinking about the desert scene.
I've done this at work today (whilst I should have been working).
All done in maya then comped together in photoshop. Basic Perlin clouds over a gradient for the sky. A heightfield terrain for the mountains. Dunes are modeled (roughly) then rendered with Mental ray sun sky. After that just a bit of colour correction in photoshop. Im kind of happy with the look but im going to add a bit rock and pebbles to give it that Chile feel rather than the Sahara look. And I will add a dune texture to the areas closest to camera.