Note: This will only work if u use a pc.
1: Log in to ur account and click 'me'
2: Click ur avatar/ or click edit.
3: Click the stick man figure.
4: Go to 'gears' (for the head.)
5: Type random letters and numbers then press the next arrow (keep doing this for each page.)
6: When u reach page four u should see a snowman head.
And there u go! A snowman head for ur avatar.
Another note: When u log in on a ds, u might not be able to see ur self with the snowman head (not sure if u will see ur self with the head but for me it didn't work. Even in chats (on the ds). Don't blame me if it doesn't work for u. Cauz it worked for me.