turn on Soft Shadows on the sun light, and add another layer of procedural to the sand material, one with additional bump.. perhaps a wavy sort of material. That should give you some ripples in the sand from wind.. APart from that.. the simplicity of this image is what does it for me :) Aside from further detail, it has a good feel. Really makes me feel like I am looking at a solitary craft in the middle of one HUGE range of dunes. Scott