Nevada was an environment where the primary shader challenges were for rock and sand. Roel Coucke did a great job on supporting a lot of the complex requirements for this, my involvement in shaders for the level was relatively light.
A lot of the organic elements of the level were all custom sculpts with unique macro textures that then went through a shared bank of tiling textures. This was effective but ended up costing us quite a bit of time! One downside of the shader setup for the map was that the sand floor shader was very expensive for all the elements in needed to support and blend between. This actually hurt us quite a lot as this shader always took up a lot of screen space.