Since we have different dog breeds, Episode should be able to add different horse breeds as well. A Draft Horse body would be good for stories where you need animals who do hard labor, and Ponies can be used by child characters.
Some examples of Draft Horses (The breed pictured in all three photos is the Clydesdale horse) :
And some ponies:
Shetland Pony
Connemara Pony
New Forest Pony