Thank you. Because he was in his mid to late 30's, his death was not unexpected, but in a way it was, because right up until the end, he was a very hot horse and could wear a rider out on a long trail ride. He was one of those horses who never wanted to come home. Certainly not barn-bound. A wonderful horse for youngsters who knew how to ride.
But now I need to ask some questions. I thought always, that to be a Paint, which is designated as a 'breed', horses had to have a known background and be registered within that registry. The OP doesn't know her horse's background, but are you saying, that if she thinks the horse is half Thoroughbred/QH, then it automatically becomes a Paint? I hope some knowledgeable people jump in here, because I've never heard of a registry which accepts the say-so of a horse's background, to be approved. We of course, except iffy dog registries which will 'register' anything.
I believe the OP can register her horse in the Pinto registry, also.
The OP's horse, appears Tobiano to me, although could carry frame, if we knew her background.
Many horses with no Arabian in their background, hold their tails flagging or high. Even some of our Gypsies do.