The color choice is really striking, but perhaps a bit too gold? I mean, it all comes down to color conditions, but perhaps the edge tint towards yellow could move in a different direction. Experiment.
The blue-green is pretty wonderful as a secondary color, though. Will be useful for rendering the jacket too.
This is a pretty inspirining piece of work, and foremost, process. Keep it up and it's getting featured. This sort of stuff is why Pixelation exists.
More bits and pieces of critique:
* Right side (ours) of the face, where the shadow of the cheek eases into the side of the nose, I think in that little gradient, you're neglecting that the nose is pretty much pyramid-shaped, so it has a \ surface there that both catches a bit more light, and even if it doesn't, really does not just gradient like a curved surface into darkness like you've got it going right now. If I am not being clear shout at me and I will do an edit.
* That mole is probably too blurry. Again, it depends on 'photography fidelity' and you can do whatever you feel like, but I'd personally sharpen that detail up a bit.
* some of the buffer shades for the highlights where you've got them all circly and rounded at the ends, perhaps it's time to start introducing just a bit more angle in there. Perhaps it's me.
* I think the expression is determination now, is that what you want? If so, good.
* Will you dither this at the end? If so, that'll be a massive stage so be prepared. And try not to lose plane distinction by oversoftening with the dithers.
* I'd suggest you start going from generic to specific in the jacket here too, just so one part of the piece doesn't overdevelop over another and they end up disagreeing.
* Nice lip highlight
As a sidenote, think about how different this is and how much you're learning through the SCIENTIFIC!!!!1 process as opposed to copying a photo like the oldschool demoscene would do. Think about why they got stuck where they were for 15 years and where you'll be with the analytical approach in 15 years. Really inspiring.