I'm no expert, but from what I can tell you look really nice. Good posture and your eyes are up. Your leg is a bit forward (if you draw a line from heal to hip to shoulder it's not quite straight). If you get your heals down a bit more that might help. They are down in this picture, but a bit more wouldn't hurt. Overall you look really good!
On your horse, I'm on my phone so I can't really tell, but it looks like you have a bit with large shanks on him. Correct me if I'm wrong. He looks like he is gaping his mouth some in response to the bit. Maybe try him in something softer such as a snaffle to see how he responds and really try to get him on the bit and working from behind. Again, the picure is kind of hard to see on my phone so I'm sorry if this is way off base. =) Posted via Mobile Device
You have a nice, vertical posture, and a nice, straight line from your elbow through the rein to the bit. I can't tell from the picture, since you're wearing a jacket - do you get a sore lower back? You might be just a tad sway-backed. You're in a little bit of a chair-seat, with your femur just looking like it's really high up there on the saddle. I'd try lowering the stirrup-leather a notch and see if that will soften the angle of your upper leg a little and let you pull your heel under your hip a little better. That should let you bring your butt just a hair further forward into the saddle into where I think the deepest part probably is hiding. Nice foot position (heel down, toe slightly out). Try a ride without stirrups and see where your butt and leg naturally lie. Nice job looking where you want to go.
Harsh critique is not intended. You look really lovely. You asked for critique, so I'll pick at anything I can find in an effort to give you anything at all to look closer at and potentially work on.
I keep looking at that left front boot on your horse, and it just doesn't look right to me. It could be because it is the picture, but it looks like it has slipped too low or twisted. The right front boot doesn't seem to match the left front. I worry about boots because they can do more harm than good to a horse's leg if they aren't put on properly or do not fit.
I agree with the poster who suggested you lower your stirrup just a little; I think that would enable you to get your leg underneath yourself a little more which would put you in a more ideal position. Your posture looks lovely! I'd like to see you with just a little more bend to your elbow, and possibly bring your elbows a little closer to your body, although what I'm seeing could be a trick of the light, I can't make up my mind!
Regarding your cute horse, I'd like to see him reaching into contact more, rather than bracing against the bit and hollowing his back. I'd bet he's a forward ride and you're used to trying to slow him down. Although it seems backwards, hot horses really need more leg, to get them to learn that they must accept leg. It looks like you have quite a bit of air between your lower leg and the horse, probably because he's hot and sensitive and he doesn't take much leg to send forward. However, holding your leg off his side is limiting his ride-ability and your level of control. Ideally, he would accept your leg more willingly and allow you to ride him from your leg into your hand. If you can get him working properly like that, he will begin to allow you to ride him into contact, rather than bracing against the bit. And as another bonus, a horse that is working properly through his back will build up a nice topline, which just makes them prettier. :)