I did not know about this coloring algorithm. It is simpler than the tip that I gave above, but in the same time it makes only frames with smooth surface. With my suggestion can be created rugged (carved) frames. By the way it can be used at any magnification of the fractal image - as bigger is the magnification as smaller are the thickness and the inner radius of the first ring in circle-limit transformation. Anyway thank you again for sharing your experience. Have a nice day.