Good work T1ck! I really like the way you are modelling this head - it's already looking very good and pretty close to the reference image.

It's early days i know, but it looks like the crease from the corner of the mouth needs a bit more definition and the chin looks like it is protruding just a touch.

This should be an interesting project and I think it would definitely be cool to do a stone version and a real 'flesh and bones' version.