I don't really like either of those edits, to be honest. I think Claredeth's is going too much into actual style than realism which is what I believe you were goin' for here, man.
Souly's is more in the right direction, as he's talking about volumes and form and chiaroscuro, that stuff.
I think you can use a similar "wrinkly, old" texture, but making it more smooth and making it not looks so flat and scribbly!
Edit of Souly and Clare's edits:
I didn't have a lot of time, but that's what I want to show you. Use wrinkly skin textures, but make them work to your advantage. Use line to show texture and wrinkles, and most importantly, think about making things clean and not so rough.
Since you talk to me on AIM anyway, ask me any questions ya' got there.
-Dex