Bill Harper has this nice pair of appaloosa mules. What a wagon! These mules are suitable for riding as well, but like most mules can pull a load too.
Donna and Leroy Thoreson, left, Glen Everts right
Big draft mules are usually out of Percheron or Belgian mares (although other breeds are often used as well) and a mammoth jack. To get a little smaller but fancier show type draft mule, the ideal jack to use on a draft mare would be just around 14 - 14:2 hands, which would add a little refinement to the mule.
A nice team of mules by the Campbell Jack, owned by Ken Heimendinger, out of Percheron/Tennesee Walking Horse mares.