All the images are from google -
I always liked the ones that are like the safari person (desert tan or camo shorts, tan shirt w/ pockets; maybe a vest w/ pockets; a safari hat, hiking boots and the horse decorated/painted like a zebra with the top portion of the tail braided below the tail bone and then "tufted out"). I used to have pics of a pony done this way, but don't have it any longer...
The farmer (complete with a dairy stool and piece of straw sticking out the side of the mouth) w/ horse dressed as a cow with an udder. To be "milked" when standing still (saw one class one time where the udder really had milk in it and the "milker" sprayed the ring steward, LOL)...
A knight and a dragon.
A zombie w/ the horse done up with all the bones (in white if a dark horse; in black if a white, cream, or grey).
A knight and a knights jousting horse.
A fireman w/ the horse as the firetruck - complete with coiled hose(s)... or race car and driver (think either NASCAR or dragsters) or Herbie the Love Bug (flint Co minis - google image)
Little BoPeep and her sheep -
Christopher Robin and Eeyore
A witch and her "familiar" - dressed as a cat.
How cute is this one?
This website is GREAT!! I LOVE the Princess and the Frog - but have no idea how you'd get the coloring off the horse for the rest of it's classes??
http://www.littlethings.com/horse-halloween-costumes/
Then I did a google search for Mini horses with costumes and the themes are many and varied!!