Ink and grease marker.
Ink and grease marker.
I've built quite a few 3D heads in Sculptris to use as a reference for DREAM THIEF. These are just a few of them. The rest are in a virtual aquarium where I spend hours staring at them, creepily.
On a side note, Sculptris is freeware (from the fine folks who gave us ZBrush) so it's a great resource for artists on a budget. Google it!