I can just imagine, if I were to volunteer in this, and use the techniques I applied to my avatar, this can look amazing. I mean, the values are already there to tweak.
Issue with that though. It will take quite a bit of time to nab every little detail (Including the overlay shortcuts); plus, I think there would be too far a leap in quality. But the main issue is I tend to procrastinate unless I'm in the fey mood to do so.
But if I were to work on it, I think you'd be amazed at how much use just the burn and dodge tools can be with subtle use of the paintbrush as well, and that's just for the clothing. A texture overlay could be applied to the background as well (stone preferably, I see), depending on what material we're working with, and then with skin texture, lots and lots of detailing with all the relevant tools, even with the beard, and that would be the trickiest part to work with. All this working in 300dpi, of course.
Now you see why I would need quite a bit of time to work on it.
ETA: I'd say I would need to reserve a day or 2 to get it done in a normal mood, about a week or 2 while lazy; or a good 5 hours straight while fey, maybe tops.
(Image saved and optimized to work with (Photoshop file), just in case.) I might show a progressive update (editing/updating the post/picture), you can review it as it progresses and I'll make adjustments if it takes longer than estimated (IE- Normal/Lazy rate).