This fractal is a julia set. The colouring is done by mapping hue to density and cycling it using modulo arithmetic. The interesting textures are generated by mapping saturation and brightness to various formulas involving the argument of the density.
This particular fractal was an attempt at doing a deep zoom into the set. It worked quite well except after a while it became increasingly difficult to choose a point in the set to follow, most eventually lead to nothing, so the zooming often needs to be dynamic. In later incarnations of my fractal algorithms I will implement such functionality.