Not of my horse... but:
(on diff background, colourized, butterfly, mane/tail painted on etc.
I use gimp. It's free and can make amazing pictures.
To all people who are new with graphics.. DO NOT buy photoshop first. Learn the basics on gimp, and some amazing graphics artists use gimp.
Photoshop is exactly the same as gimp, but its $100 more. O_o