More ideas (as if you need them)
~ Eventing horse; one polo wrap, one bell boot, one cross country boot, one open front boot, carrying three saddles, with the rider in a top hat, XC vest, and water wings, carrying three bridles, perhaps even with a broken arm? Both gung-ho to do it all again next weekend!
~ "Medicine Hat" horse with Rx written on his ears, and a doctor's outfit?
~ "Trick pony" standing upright on one hoof on a ball, balancing spinning plates on his two front hooves, and a ball on his nose
~ "Gaming horse" playing poker with his buddies in the middle of a poles course
~ "Puppy-like personality" with a horse on the end of a lead, sitting and panting
~ "Typical Arabian" (no offense!) with the Arab on the other side of the ring, shaking, with the rider still hovering in riding position; play on the Arab-Teleportation thing.
~ "Hunting horse" with camoflage on.
~ "Mareish"; mare flirting with geldings on the other side of the fence.
~ " Not studdy" - stallion flirting with the mares, flexing his muscles.