I can't decide if this horse has overall good conformation, or bad. I might be interested in buying this horse as a youth 4-H project for me, but I'm not going to spend my own money on a horse that has conformational flaws that will affect his training and athletic ability.
Gizmo is a 4 1/2 - 6 year old paint gelding- not shure of his true breed, as he doesn't have papers, neither his sire or dam have papers, and nothing is known of his background. He has never been ridden before, and is thought to have been neglected before as the current owner said he looked skinny when he arrived to her. The owner said he has been seen by vets two or three times since he was with her, and they all said he was healthy, on a good diet, and perfectly sound, no problems.
When I look at him, I notice mainly the shape and angle of his croup and hindquarters, and the angle and slope of his hind legs. In my opinion, his whole back half looks very weird and out of place, not disproportionate, just awkward looking.
To me, his shoulder looks pretty upright, but maybe it's just me or I'm looking at it wrong.
Obviously, his muscling isn't the best, but he's young, and never been ridden or really worked before. I'm shure with proper conditioning and routine exercise, he will look and feel much better, but all that work can't change his conformation, build or frame.
He is quite sickle-hocked in the back, which would make his hindend look off. Not a badly shaped butt, however.
His shoulder is upright, which makes his neck tie in high.
Front legs appear alright and as you said, he could use muscle.
He is what I call "weedy" looking. His neck is a bit ewe and his hind leg has poor angles which is coupled with a hind leg with poor angles. His shoulder is very upright and I wonder if he is not a bit rough to ride.
All that being said, what do you want to do with him? If all you are going to do is trail ride, he is probably OK. OTOH if you want to take him to serious level of anything, he probably will not excel.
BTW if he is 6 years old, and looks like this.. he is weedy. If he is 2 years old and looks like this he needs time to grow into his body and might be OK. At 6, not so much.