Conformation critique & breed speculation, please? (pic included)?

((I am having the worst time getting this question to actually appear in the section and/or have the image link actually work. Major apologies for the redundancy if this ends up double/triple/etc-posted.))

My trainer got a new horse in for me to ride. He's very green, but really fun and so sweet. It sounds like he came from a bit of a shady background, or at best some people who just didn't understand that he hated the jobs they were having him do (barrel racing, then endurance races). That and couldn't keep weight on him, as the lady who now owns him and is leasing to my trainer had to take a year to get him back up to weight, I'm told.

He's now learning about indoor arenas, balancing a rider around corners, and carrying a rider over a small line of fences. He's a little sensitive, but has a good brain and tries hard.

This is just a quick picture snapped with a phone after my lesson/his bath, so sorry he is not stood up squarely, but any comments on his conformation? I have my own guesses, but I like hearing others' input to sharpen my eye.

((Image link will be added momentarily, as I believe this is what is keeping the question from posting properly.))

He looks rather warmblood-y to me, but he doesn't have a brand and I'm doubtful someone would have grabbed a WB and had their first thought be "barrel racer!" I'm guessing on a stocky TB or a larger QH, or some mix of the two/three/something else. And theories (and why)?

Thanks everyone!