Definitely need to work in the grimacing, keep your face relaxed as best as possible
Bend in the legs looks good.
Front and Side relaxed - don't crunch down on abs (I am not saying to be loose, definitely keep the abs tight, but not at the expense of keeping chest high)
Rear relaxed - spread your lats, don't crunch shoulder blades
Side Chest - this is minor, but it looks like you are flipping off the camera, watch your fingers
Side Tri - keep shoulder pulled back to spread the chest
I would personally bend the legs more in both side poses