I have been asked if I painted horses quite a few times (also rabbits, fish, and even snakes).
I have always declined because I was thinking you need to be very sure of the muscular skeletal structure of the animal. But really they are all the same, except the shapes change! So curiosity got the better of me, and I was ready to take the challenge. No problem. The most complicated thing (for me) was to put together a group of animals that were different sizes, ages and kept in different paddocks. You could not see them all together. Also with the varied locations the lighting direction also varies. The biggest challenge was to make them appear natural as a group.
So now… yes I paint horses. And other animals too, so if you have an unusual pet, I am the portrait artist for you!
Prices and timing remain in keeping with dogs and cats, but the proportions may create slight variations.