where can I download or create materials to create landscapes

I am trying to create a desert theme for my race car game and I need a material to place in my game that looks like sand or dirt just something that will make it feel like a desert

just wondering if theres a place I can buy or download materials or even create materials to place into my game

please help

if you are new to level material usage, you may want to take a look at the content exemple project and open the landscape level of the project.
you ll find plenty of usfull stuff in there (material layers, even a road spline)
if your looking for specific material, you ll better do it yourself with custom textures you have and modify them in photoshop.
you 'll find free of use textures here : Your #1 vray material resource | vray-materials.de