-the line from his mouth to your elbows should be the same, in this picture it is broken.
-thumbs on top instead of pointing in.
-lighten your hold on the reins a bit, particularly the inside rein. If you need to get more contact, move your hands out instead of back.
-relax in your arms/shoulders and roll your shoulder blades back.
can't really critique this one unless I know if you are in 2 point or if you're posting.
-you have a chair seat in this picture, try to sit more on your seat bones/pelvis instead of your butt.
-the saddle looks a little small on you, again I'd say lengthen your stirrups if you can bear it.
-lean back and open your chest and shoulders.
same as picture 1 pretty much.
-lean back and open your chest/shoulders.
-try to move your hips deep and with his movement.
-avoid perching on your hands, and loosen the grip on the reins if you can.
-your arms are clenching, they should be loose and move with his neck in the canter.
"The trouble with the world is that the stupid are certain and the intelligent are full of doubt"