Practice doing copy camera work? Looks like you got the tonality pretty good. Do a little research on the lighting setups for copying and you can get it down perfect.
Sorry my friend, this is a PHOTOGRAPHY related site, not drawing/painting/printmaking/ect. There are several other sites where you could post images like this and probably get ALOT better feedback from people who are working in the same media
i think marko asked the other day if it would be okay to post some of his sketches in the gallery, and the folks that responded to his question said it was okay ...
marko, if you get too much grief posting here, you could probably "afix" your sketches to a post .