I've been staring at those pics all the while modelling it and i still couldn't honestly tell you. There are parts of the forehead that are bolted on and shapes that look more 'regular', like panelling, yet those same organic areas also have some asymetry to them. If organic, I imagine the tops of their heads may be chitinous, like shellfish?
Anyhow, here's some further progress:
I'm getting to the stage where changes are getting to be a lot smaller, a lot more subtle. I spent some time getting the angles and proportions a bit more accurate and have started adding in smaller details around the eyes. The model is still largely mirrored, so I want to get all the main symmetrical details down before proceeding with the asymmetric details. The cheekbones are a bit more rounded, i've started adding the little 'straps' that come off the mask (although they should be more of a boney material, NOT the dark metal pictured here). I moved the entire top part down a bit and moved the eyes up a bit to better match the overall placement of the ears. I'm not going to model in the downward tilt of the ear greeblies - from what I can tell, those pieces are part of a leather cowl worn underneath and they may well sit tilted on their own.
I have not yet corrected the height of the piece that sits on the back of the head, but this should give you an idea of where I'm sitting silhouette-wise.
I can see i have a slight symmetry problem with this back view, which will be pretty simple to fix, provided I remember to do so.
And here's where I'm at with the ear greeblies currently.
As far as printing -
Predatormv: Thanks for the offer! I am currently looking forward to a change of residence within the next month or so, and do have a printer on order, hopefully arriving some time in March. I'm not sure whether I'll have something printable by the time i'm all settled in, but if things fall through, I know who to talk to