I have created a head from a scan and placed an existing skull file in side it. I believe the skull was originally this one - http://grabcad.com/library/skull-1 although I got it from here: http://www.thingiverse.com/thing:43591 and I have done a bit of refining and tweaking to the STL file.Can be made as the assembly when made using a technology that allows for visible internal detail (Polyjet, SLA, etc). Or maybe you just want to make the skull or just the outer head.