I judge horses based on the skeletal structure - we call this "Functional Conformation". It's based on studying many different disciplines and then applying the knowledge of horse a horse moves, why he moves that way, and what is causing him to move that way. Do keep that in mind, as many people judge conformation in many different ways(particularly the "uphill v. downhill" debate), but I've found this to be the most scientifically sound and best explained method so far that actually gives results. If you're interested in what exactly it is, here's the basic PDF guide on functional conformation: https://www.hcbc.ca/wp-content/uploa...t-revision.pdf
First off, your youngster is rather butthigh but that's just a growing stage, so unless the dam and sire are butthigh I wouldn't worry about it. He'll level out once he starts maturing a bit more. He has a good neck emergence, located above the point of shoulder. According to functional conformation, this is one of the "big three" that we use to tell if a horse is uphill or downhill. A horse with a neck emergence lower than the point of shoulder will have more trouble lightening his forehand and shifting weight back on to the hindquarters - which is essential for longevity, as a rider adding weight to the horse's back and the unnatural position that many horses are ridden in causes the back to hollow, head to raise, and stride to shorten, in turn causing more impaction on the spine and eventually even can be the cause of kissing spine and other issues. In functional conformation, we judge based on how well a horse can do it's job without pain or hindrance due to conformation.
One fault this is poking out to me is that he's sickle hocked. In my opinion, I'd rather have a slightly post-legged horse than a sickle hocked one due to the fact that sickle hocks add more strain to the horse's tendons and ligaments, since he cannot align the bony column under himself to help hold himself up - he would have to stand camped out to get his hocks angled correctly, and then that would defeat the purpose as the legs are too far out behind him to hold a considerable amount of weight. Your horse only appears a slighter degree sickle hocked, as long as his health is taken into considerable and he's not pushed beyond his limits I think he'll be fine. Post-legged should also be defined from being sickle hocked - post-legged refers to the too-straight angulation of the hock, while sickle hocked is the over-angulation of the hock. For comparison: http://cruzminihorses.com/images/min...358x167_1_.jpg
He also lacks musculature on the neck, which makes him appear to be slightly ewe necked but I don't think he has a true ewe neck. It looks like a muscling issue rather than a skeletal issue to my eyes. (Do consider though, a young horse will often be poorly muscled until he fills out a bit more so this is nothing to be worried about or out of the ordinary. If he continues to have an incorrectly muscled neck throughout his life it's likely due to a high and tense headset, and training will be needed to teach him to relax and stretch out some.)
Overall, he has a nice uphill build. I'd be very excited to see how he fills out and what he looks like as a better muscled 2 or 3 year old, even with the sometimes gangly gaited horse type he looks like he'll turn out nicely with correct work. ;) His cannons are slightly long for my taste personally, but that's nothing that will affect him in work really unless you're planning on GP dressage. :)