In most of the pictures, your leg is very far back and your heel is up. I think you should shorten your stirrups a hole so you can stretch down your heels and keep your leg underneath you. You are slouching, so remember to keep your back straight. I like your elbow, it has nice bend, and your thumbs are on top. Remember to look up! You seem pretty good about that, though.
Pic 1: Pretty nice. Your release is a bit off, though. It isn't an actual release, you are just putting your hands down, which is restrictive. I would suggest a long crest release, where you put your hands halfway up your horses neck, and rest your hands on thier crest. This will in turn support your leg, which looks pretty good here. I would be wary about you putting your bottom back into the saddle to fast, but I can't say anything without seeing you ride.
Pic 2: Again, you are restricting your horse with your release, but better than the first picture. You have most of your weight in your knee, which causes you to pinch and lets your leg swing back. I think you should shorten your stirrups a hole or two.
Pic 3: Your horse looks adorable here! Your release is better, but your leg is slipping back still because of your knee. I like everything else, though. Don't worry, I have the same problem. Her braids look great!
Pic 4: The timing of the picture always makes a person's EQ look subpar, so I won't critique this. The best pictures are taken JUST as the horses hind legs leave the ground, and she's still taking off here.
You and your horse are super cute!