My little man was a Deer/caribou/moose and I was the hunter.
I cut out about 1.5-2ft long antlers out of cardboard and plopped them on his head the day of the show (which, for a 5 year old is a huge no no, always try the costume on and get the horse used to it) of course he didn't care long as he didn't get poked by anything. Then on his back I did spotslike a little fawn, and put orange duct tape around his boots to make him "visible" also having an orange browband made it cute as well, lastly on him I put orange vet wrap on the base of his tail.
For me I was in normal black jods, with a camo long sleeved shirt, with my helmet- with orange vet wrap on it, in orange chuck converses (hi-topsoh yeah.) and black eye shadow under my eyes.
EVerybody LOVED it, and thought he was the most cute thing in the world- except the girl who got second in the class ;D I wish I was going again this year and I would put huge wings on him and me be some sort of goddess but I'm lacking a horse trailer xD