I think you have a terrific foundation for cross country riding. Your lower leg is dead solid perfect, and your base is out of the saddle exactly the right amount; with your crotch over the middle of your saddle, unlike the common flaw seen in a lot of hunter riders of standing in the stirrup and laying on the neck.
Your photo is a great example of the principle of equitation that if I could make your horse disappear out from under you and you dropped to the ground, you would land on your feet, balanced, absorbing the shock in you ankle, knee and hip.
This is even more praise worthy when we look at your horse, who is round as a ball, and has really cracked his back taking a good look at this scary XC fence. He's making the kind of effort that distorts other rider's positions.
You're wearing your stirrup slightly farther back than is considered correct for hunter seat equitation, but it is still functional, allowing you flexibility in your ankle and depth in your heel, but more security than the equitation ball of the foot position.
Now, for the quibbles. And they are quibbles, because over all, your an admirably strong, functional rider. You have a noticable hollow in your lower back, definitely a hunter ring mannerism. If you start riding cross country or eventing seriously, you'll find that position tiring. However, hollow back usually creates a locked hip; and yours is definitely not. So this is more in the category of mannerism than serious form flaw.
Your "chicken wings" are in part produced by your dependence on the traditional hunter ring crest release. Artificially reaching down and in with your hands makes your elbows pop out. Also, because your horse is so round, and making a big gesture with his head and neck, your release is too high and floating above the horse's neck. I can see your off side hand from this side.
You are certainly not restricting him in any way, so this mostly falls in the realm of mannerism rather than flaw as well. If you were doing more than playing, I'd encourage to work towards an auto release. At Training Level and above, you need the extra control and influence an auto release provides.
I'd love to photo shop this and drop your hand down and tuck your elbow in.
The overall impression is of a strong, capable rider on an athletic, willing horse.
You should event!