Character model changer

Hello. i wonder if anyone knows if it's agenst blizzard's rules to change your character model to something else by an addon that only you see nobody else. For exaple let's say your an Night Elf and want to look like a Human? is it agenst blizz rule's to use a addon that changes that or is it possible to use it and it's okey? And dose anyone know where i can find those addons?

Cheers.