There are a few things I'd improve on (I actually recall seeing you briefly at the con.) It was good for a first attempt.
Lets start with something basic. Makeup. Light brown eyeliner and shadow can be used to add the wrinkle effect. The same type of supplies can be used to add the liver spots on his face. He also has eyeliner (what anime doesnt) that could go down in to the 4 lines beneath each eye. But those could also be really weird wrinkles......its debatable.
The next thing is the head and arm armor. The plates should be a green/gray with hoops connecting each piece. The head piece should also sit low enough to cover the majority of the eyebrows.
Sleeves! The black sleeves should end beneath your elbow and bunch up as if tucked in. (or tightened with elastic) The fishnet should start beneath the black and continue only to the wrist, where there should be a thick black band. There should also be a gray lining to the fishnet. It isn't just on top of the skin. If you want something light weight and skin fitting you could use cut up tights beneath the fishnet. This method could be used on both the arms and legs. (Though one could simply use footless tights on the bottom)
The only other thing you might want to improve on is the shoulder piece. It doesn't look like it is supposed to be fabric, more like a hard armor piece. Perhaps this could be made out of wonderflex, but looking at all armor methods could help you. (I've never personally made anything armor related so I cant help any)