Unfortunately my computer crashed right after the PNG export and of course I forgot to save the PSD document :/.
There where not many more in between steps, but they are lost. I did the following:
I duplicated the creature layer twice, and made a selection of the creature. One layer i filled with black, the other one with white. I set the blend modes to screen and multiply. I then masked out parts of these layers, to create hightlights and shadows.
I then made the creatures shadow on a layer set to multiply.
I then applied a levels adjustment, and two layers of color. One light bronwnish set to color blend mode, and one blueish set to overlay.