I got a couple requests for "how" I painted the pale skin on the Raven Guard guys I've been working on lately. It's real simple and if you take your time and work in the details of the face and blend your highlights, the results are better than tabletop.
It's just one color (a light, cool grey) and two washes, Ogryn Flesh and Devlan Mud. Here's the process.
1. Prime. I did this one in black like I did the others for consistency.
2. Basecoat with the light grey. You want a nice, smooth and consistent finish with this coat.
3. Liberal wash with undiluted Ogryn Flesh over the face.
4. Go back with the grey and pick out the raised areas of the face.
5. Slightly thinned (50/50) wash with Devlan Mud over the face.
6. Go back with the grey and pick out the highlights.
Like I said, if you've got a good, smooth basecoat and you take your time working with the grey, you'll have some really nice transitions on the face and plenty of detail.
When I'm working with the grey, I thin it down ever so slightly so that it takes two coats to get it back to pure grey when I paint over another color. Make sure your final highights are that pure grey too.
UPDATE: Some additional links that might help.
A tutorial for Dark Eldar skin tones and tattoos
How to paint rich, vibrant skin tones