Deserts/ Sand and Canyons

Hi, I’ve been playing around with sand textures for a while now and I’ve gotten this far, but it still doesn’t look quite right, so I’m wondering if anyone has any knowledge or experience in creating realistic looking deserts.
http://img513.imageshack.us/img513/511/sandyo0.jpg
http://img524.imageshack.us/img524/9120/desertso4.jpg
http://img517.imageshack.us/img517/8977/scastledeserttest1oo5.jpg

While I’m posting this I’ll also ask about canyons and cliffs which I haven’t done as much research into as with the sand.

There are several desert environments in the film I’m directing so any advice on how to make them look more realistic will be greatly appreciated.

Your sand is way better than you think, it’ll look much better with good lighting:

http://www.itchy-animation.co.uk/light.htm

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From a structural aspect, I can see a lack of regularity in your dunes. Large expanses of sand generally take on a regular 'wavy" pattern depending on the direction and strength or the prevailing winds. Dunes also exhibit smaller ‘rippling’ patterns as well as ‘crescent shaped’ areas on the leeward (away from the wind) side where the slope of the dune is generally steeper.

Here’s a link or two you may find useful: http://www.desertusa.com/magjan98/dunes/jan_dune1.html
and http://pubs.usgs.gov/gip/deserts/dunes/

You’re going to have to find a way to introduce depth of field and aerial perspective (the effect of colours becoming less saturated and usually bluer further in the distance.). Currently the foreground looks like it’s just a hand-span from the background rather than kilometres away.

The large brown hill wouldn’t be that richly coloured in real life. It would more likely be purple-ish. Atmosphere is a big contributor to large-scale images.

Plus, as Fligh said, you need good lighting that adequately simulates the outdoors.