Those pictures are helpful...and I like him - it looks like you've got yourself a nice little horse. More pictures confirm he could use a few pounds...just go slow - they don't get skinny overnight, they don't need to put it on overnight!
He definitely looks like a paint - I see his markings there under winter's decorations! Paint horses are a coat pattern with large areas of color (black/white, brown/white, gray/white etc) - and they have their own registry (if he's registered - which is unimportant for a companion/riding horse - this is just to give you some more info). So paint is a coat pattern - the same as many dogs have the black and tan coat pattern of many Dobermans, Rottweilers, Min Pins, etc. and it would be as if they created a registry for all black and tan dogs - regardless of the breed. This is what the Paint horse registry has done...many breeds can be registered as a paint.
American Saddlebred - Paint
Quarter Horse type paint
Thoroughbred paint
The same can be said of Appaloosas....coat pattern that can be registered in both the Appaloosa Registry (meeting lot 'o criteria like the paints) as well as whatever their other breed is.
Not sure of the breed but he is of Thoroughbred type, but here is Pay-n-Go, an
...and here is a quarter horse type appaloosa
Someone with paint or appaloosa experience can tell you more about both breeds as well as what your horse is - especially when he sheds out in spring and has a healthier coat from the better diet you are providing.
I just wanted to give you this info so you could better answer peoples questions about him through the years
