It's a little hard to see these pictures, but I'll try my best.
In some of the pictures, it looks like your heels have slid up.
Your hand, arm, and elbow positions look pretty consistent. In the last picture your elbows and arms look a little funky.
Over all, you seem to sit up nicely and your back looks fairly straight, except for your shoulders, which seem to curl forward now and then.
You seem to be looking down in a few pictures.
Your leg position is a little inconsistent. In some pictures I like it, in others it seems to have slid back.
Again, it's hard to tell with these pictures, so sorry if I'm way off base!