As per usual I will start with this disclaimer; I am not an expert, I would appreciate being corrected whenever I am wrong! What I say is tentative, there are tons of more educated people on here to give you a better critique.
He has average-looking bone (?), short and well-sloped pasterns, both front and back, and nice short canon bones with round, low-set hocks.
He looks a bit behind the knee, and maybe a tad over- I'm not entirely sure because the mottled grass makes it a bit hard for me to make out the lines...
His back legs look pretty perfect to me, and I really love his back end- strong, big hip, although his croup is a bit short and high.
He has a nice deep girth, a well shaped shoulder, although I think it could be a bit bigger and might be a bit steep of angle, and his neck may be just a bit short. His back looks a bit long but nothing to worry about.
Overall, I think he's very lovely- I love how he fits together overall, he looks balanced and pretty level, maybe very very slightly downhill, since he is a thoroughbred and he looks like he has some pretty high withers... But he is quite beautiful.
And he has such a pretty coat, that's a plus! ;)
Anyway, he sounds like a doll! Congratulations on finding a horse that you really enjoy being with!