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Here are some early camel drawings and rug patterns; I found coloured pencils brought out the surface of the paper underneath which created quite a believable fabric texture:
I added colour as well as textures, experimenting with various implements and techniques until I got the hot, dusty atmosphere I desired:
I incorporated my rug patterns into the drawings:
I experimented with different ways of drawing the camels. The elongated shadows and different viewpoints can make the desert seem a very alien environment, especially at sunset:
I focused on the foreground details and textures for some up-close camels:
The final composition: (click for larger view!)
2012 Edit: The evolution of a project! This is a good step by step example of how I work and progress through a project, from early drawings, to experimental stages, to producing many studies of the subject before selecting the best to use for the final illustration(s).