This is the ultimate cubic fractal, each face will be completely covered with child cubes of all the following recursion levels. This was tough to figure out as I am not used to the declarative programming style used by OpenSCAD, but eventually it worked. The fractal will get a whole lot more complex with each additional recursion step and takes ages to render(quite literally if you overdo it...). In mathematical terms this is the quadratic Koch curve extended in the third dimension: http://en.wikipedia.org/wiki/Koch_snowflake