Unfortunately I am not good at judging artwork. I like the last one best because it is the most realistic. As far as I am concerned they are all great but I could not pass a matchbook cover art test if I tried.
Also unfortunetly the most common model was a man, but when you're drawing it's just about the lines (a bit of a shock at first). I didn't part "the parts" btw... A.) it made me feel kinda weird and B.) now they're just PG-13 instead of R.
The pic probably won't show... You can copy it and paste into another window probably. I'm leaving in a sec and don't have time to host the image on a non-geocities site.