I was looking at it today, and decided to replace the portion that's setting up the distance equations with what started as a torus. Yesterday, when manipulating a torus in another program, I noticed how when repeating the torus with a sin or cos, and tweaking other parameters, the general shape was very "clod-like". This made me interested to see how the same equation would look with the clod coloring and lighting scheme.
I wound up really liking it.
I included the optimization by iq, which removes the break from the loop that does the ray marching. I decided to let the mouse/trackpad influence the camera viewpoint as well as the distance equation. I also ended up adding a vignette function.