1. Your horse has really nice leg extension, but he's working off the forehand. Use lots of leg to push him through his hind end so that his impulsion come up through his hindquarters and back. You have very nice position by the way! Loosen your reins a bit and allow him to work into
2. He needs more weight and muscle. Lots of trot-work helps with improving topline and rump muscle. His neck is a bit thin, but this will probably improve with more muscling. He has a very sweet face.
3. His confo looks a lot better in this picture. Was it taken sometime later? He looks a lot more muscled to me but his rump still needs a bit more work. Try not to force his head into a frame. I know you were probably doing that for the picture, but try not to focus on his head too much when riding. Work on his back end first.
4. A little more release. Look up.
5. It looks like you're jumping "for" him in this picture. You have beautiful leg position and natural form ... but try to close that gap between the saddle a little more.
Those are just a few things I've noticed. You guys look great though. Keep up the good work!