Alright, it looks gr8 any ways man, try looking at some tutorials of photorealistic skin, i saw a zbrush workshops one but never got arround to get one...
Might be as simple as adding a pass for SSS (Sub Surface Scattering). Also, you may want to revisit the ZBrush Summit's presentation by the two judges of Face Off. Glenn stated that you want to start off with you're lightest shade first and progressively get darker. I know he was making a demon, but the process should be the same.