To my newbie eyes, I think that the foot relies too much on construction. The toes are boxy and don't look like they're pushing off the ground. I'm also uncertain about the lighting / shadows -- the first one I noticed was the cast shadow on the floor. The hand looks pretty good! Seems like an interesting top-down perspective but again the cast shadow and linework needs more effort. I like it the best out of the three you posted. I think it has the best use of tones! The portrait has interesting facial structure but could definitely use more work with shading, particularly the forehead highlight. I think without that 'U' shape and more subtle hair highlights it could look like his half face is in a cast shadow. Not sure if that was intended. Overall, I think more focus on carefully developing tones and lines with a better idea of the environmental context would really help. These are very interesting images you've chosen to ask critique for -- all great attempts ^-^