The dog could be laying down, with his head resting out in front of him on the ground, sorta giving a "peak" up at the horse. The cat could be brushing up under/ against the horse's face or jaw area and inquisitively reaching his nose out to the horse.
It looks wonderful so far, I am sure that whatever you decide will look great! :)
"Horses don’t have hard mouths, they have hard, stiff bodies. The softer you can get the horse through his body, the softer he will be in your hands." Clinton Anderson