What do I get for WOW Christmas? Could Santa please get me Extra Hearth Stones, One for THunder Bluff and one for Undercity?
BTW if you have ever played FF14 you would like it as the king of Transportation, the aether stone.
You will get any drops you get from the Greench, be sure to kill him every day! See a list of possible drops here: https://www.wowhead.com/npc=54499/the-abominable-greench
Additionally each year there is typically a new battle robot toy under the tree on Christmas day! There will also be some other presents, which sometimes include previous years toys.
Be sure to do the initial quest, too, for the Winter Veil Disguise Kit. 
Here’s the full rundown: https://www.wowhead.com/guide/world-events/holidays/feast-of-winter-veil
Happy holidays!