your shoulders need to be back a bit more (i have the same problem don't worry) get into the habit of having them back by rolling the back as you remember throughout the day. Also although that looks like a dressage saddle, I feel like your stirrups could be up a hole or two but that might just be the hunter in me...
No puppy dog hands! Thumbs to the sky!
Other than that you look great!
Equestrianism; 10% luck, 20% skill, 15% concentrated power of will, 5% pleasure, 50% pain and 100% reason to remember you're absolutely insane to be riding a beast that big.