I think you could get away with 3 different body styles, possibly 4.
To keep me from using an actual breed name in place of a group of horses, I’m gonna switch to three different terms: coldblood, warmblood, and hotblood. These haven’t been used so far, so I hope I don’t confuse you more. Just think that all horse BREEDS fit in ONE of these three categories. It’s kind of like, but not exactly, Bantams and Large Fowl.
COLDBLOOD — these are your Work (or Draft) Horses, the large horses with a heavier structure, and huge, broad feet, like your
Clydesdale. Generally a very calm horse.
HOTBLOOD — these are your “fast and flighty” horses, the thinner race horses like the
Thoroughbred.
Arabians are also Hotbloods.
WARMBLOOD — these horses are a combination of the Hot and Coldbloods. They have the best traits of both. The Warmblood has the muscular build of the Coldbloods and the speed of the Hotbloods. This group would include your
Quarter Horses, Paints, Tennessee Walking Horses.
Pony — this could be your 4th body type, a smaller version of the Warmblood would be perfect.
Shetlands and
Welches are both ponies.
This graphic shows three different body builds in each type. Maybe you can use the
Average build as your model.
View attachment 2512634
[Maybe these next two graphics will help you with some of the things that were mentioned by others earlier.]
This describes the particular COLORS of some popular breeds.
View attachment 2512636
Someone mentioned the coloring on the legs earlier. I call the color, stockings. Some horses have them and some don’t. But if a customer mentions their horse has a star with a stocking on their left back leg, you will know what they mean and what you should draw. They will need to specify how tall the “stocking” is. (I’m not sure how many will actually use the terms mid cannon, half pastern, crown or coronet. Maybe they’re more used than I’m aware of.)
View attachment 2512635
I have 6 horses, but I don’t have a good variant of colors. I have one Bay and the other 5 are Sorrels. Three are actually Paints, but not your typical Paint. They each have just enough of white patches to qualify them as a Paint in the APHA registry.
I hope this helps a little bit more. I wish you much success with your artistic abilities!