quality stuff dude! browsing through some of your pages and i see you dabble a lot in varying mediums-- that's great! good to see some experimentations... :3
one thing that i'd like to suggest is that perhaps in some of your still life studies you can push the darker values even more-- you seem to understand mid-tones and light/highlights-- but to create more sense of form the darks need to be darker!
good stuff all around. keep studying!! i have to do some hardcore studies as well~