Instead of the Ambient color being black, try going up a couple shades of grey. This will bring out more brightness in the texture but don't go too high, or it'll start washing out the texture. Also, some maps are designed with crazy lighting systems in use during testing. Try adding a couple of lights or increasing existing light's intensity. Some of the commercial maps I've seen from here have some strange ideas of realistic skin pigment, this you can correct in photoshop with hue/saturation or Brightness/contrast. Good luck, hope i helped. -WTB