I hesitate to post the next raytracer image, since it's not quite much to look at yet compared to the terrestrial and Jovian images, but what the hey.
Yes, trying to create a decent cratered moon. Currently, I'm planting 100 randomly sized craters around the globe. 12 of them are maria (lunar seas), areas where a very large object would have hit the moon and caused lava to spill out, darkening the crater's interior. The age of each crater is also randomly chosen, so they can overlap and obliterate each other -- the maria are set to be very old, as such impacts would presumably happen early in the moon's formation when more large objects are still floating around the solar system. The radius of the craters is distorted based on a value extracted from a fractal sphere, so they aren't perfectly circular.
The next trick, rather than just coloring the ground based on the crater's presence, would presumably be to change the surface normals instead, so the craters have a rim and/or central peak as needed. If a standard fractal landscape is also thrown in behind the craters that might create the appearance I'm going for. (Hey electroweak, what were those rules for crater formation again...?)