Really cool Ivancic, glad you are taking a jump into the modding!
Yeah Matt said everything I could think of, except you might need Zbrush (at least I think this is what the team uses) or Autodesk Mudbox to sculpt out those heads and details going into them.
Rad did this, I think those 3 heads to right goes from 3ds Max, Zbrush (to make those cool details), and the texture with Photoshop.
Another one