With my 29th custom I got into custom swaps. The idea behind these swaps is to pick a theme, to send in your specific preferences within that theme, and to create a custom based on your partner's preferences. You then send off the custom you made and wait to receive the custom that your partner made in return. It can be a really fun and rewarding experience.
Frosty is a bit more complex, and was made for the Arena Xmas custom swap of 2007. She was given a gradient dye on her muzzle and legs. Her hair was DH Cherry Pie, Sunlight, Poison Ivy, and Bobby Blue. Her symbol was repainted, as were her eyes.
(see more of Elf's swap and Holiday customs on her DA page.)