seperated the skull from the background, applied color changes and reduced the shadows some

then applied a plastic wrap filter

Not much of a step by step i know but i move fairly quickly from step to step with randomness. In truth I went into this pic with the intent to make the skull seem as if it were made of ice. While playing with the colors after the plastic wrap filter I changed my mind. Playing with the blending modes I brought back some of the skulls detail to give it a more solid look then did more color changes and hand doctoring until I was happy with the result. Not much of a step by step i know but I'm pretty random and move fairly quickly from step to step.