There are a lot of really great things to your postion! I love the way your stirrup is angled across your foot with your heel stretched down I love that your back is flat and you are looking up across your jump.
A few things to work on, the main thing I see is that you grip with your knees which has caused your lower leg to pivot back. Your stirrup leather should hang straight down with your leg at the girth. Do you see how it's swung back? So you need to redistribute your leg pressure so you have even contact from your calf, knee, and thigh. It also looks like you may ahve lost some contact through your calf because of your knee. Think about being wrapped around your horse, not sitting on top. I'd also watch your release. It's a good start to a crest release but your wrists need to be straight and your hands resting on the crest for your body to really be relying on a proper release. Sure, your shoulders are a little rounded over and you are high out of the saddle but often when you fix your leg upper body positions tend to fix themselves. Good start so far and very cute pony!