great work! can you tell us a little bit about how you lit this scene to get the nice highlights, as well as the materials you use to get the specular highlights? I’m assuming you also use projection master for the finer details like wrinkles?
have you done any test renders outside of ZBrush? I find that getting this level of detail to show up well in an outside program (I use Maya) is an art form in itself!!! 
If I had one piece of constructive criticism, it would be this - try to vary the size of the wrinkles. Look at older men with wrinkled skin and you’ll see that the wrinkles can vary greatly in size, width, and length. This will make an already awesome piece even more life-like! Hope this helps:lol:
I wish you luck in your endeavors!
Mike