I found a cool little trick in Carrara that I thought I'd share with you. I took a texture from that cgtexture site that was mentioned previously and opened it in Photoshop. I converted a copy of the texture into grayscale and applied a gaussian blur of about 3 pixels. I opened up Carrara and added a couple of sphere primitives to the scene and added a finite plane for the ground. I added a realistic sky background with skylight for a Global Illumination effect.   I took the texture previously prepared in PS and added it to the displacement channel in the sphere's shader. I took the original texture and applied it in the color channel, made a copy of the sphere, reduced the size slightly, moved it upward, and rotated it about 45 degrees.   I added another prepared texture to displace and color the finite plane, added a little tree for scale, hit the render button, and viola!  I'm stoked at how well the textures and displacement wrap around the Carrara primitives. The actual geometry of the sphere is being changed by the displacement maps so you can have realistic shadows and lighting. The whole procedure is dead simple and took about 30 mouse button clicks including the image prep in PS. I think it makes a really cool looking rock formation. What do you think?   The pictures show the spheres and plane before and after rendering. If you like, I can write up a tutorial of this and other tricks I've learned. Here is the before showing wireframe view...