"It's a proto-drake! Congrats on your new mount!"
"Our condolences on your recent ninja attack. Here's wishing you all the best loot in the future."
"Thanks for all your help with the raid-leading! You're the best!"
"Will you BEE our Tank?" (And there's a picture of a bee on it.)
Ok, so those aren't that great. But what other ideas might Hallmark be interested in if they were designing a new line of greeting cards for you to give out to fellow players afflicted by what happens in Azeroth?