This is just for the Christmas season, it's more of a replacement than an addition. All existing smilies are replaced with Xmas variants. Hope that adds to the Xmas feel. They'll be reverted back in Jan.
(Please note you might need to clear your browser's cache if you still don't see them. Hit Shift + F5 for a skip cache refresh.)
Also, if you have any requests for more smilies, you can always write us back.