I can see a great modelling, but i have some critics about the maps you created for all the image.
For example, you did a great diffuse map for the face but your specular map is lacking of depth, try some aging like you did in your model. Maybe increasing the contrast between the beard section and the chin area, lips and nose.
Also I would say that try for the jacket using a specular map too, and a bump map, very subtle one, leave all the leather detail to be reflected from the fill and key lights, this way is much more realistic.
Also for the cap, de frontal part where the skull is located, is just a shader, if you are not trying to achieve everything in 3D, maybe correcting it in photoshop should be the answer. I hope it works
PS. Try weathering