Wowhead has a report and several screens that have been datamined from the World of Warcraft: Warlords of Draenor beta that shows the Robin Williams memorial. The information was datamined by beta players. After Williams' death last month, Blizzard confirmed that it would memorialize him in WoW and it has kept its word.
You can summon Robin by rubbing the Ever-Burning Lamp. When first summoned, he exclaims "INFINITE COSMIC POWER" and then shrinks and waves goodbye, saying "itty bitty living space."
Nearby is a large broken egg, a tribute to the character Mork. We have datamined an alternate version of Robin dressed like Mork with overalls, so perhaps he will make an appearance here as well.
There are also some stuffed animals and tanks, hinting at a potential tribute to Toys. Our third datamined Robin NPC is also dressed like Mrs. Doubtfire.
Finally, we have datamined a Comedian title--it currently has no source, but it would be fitting if it was tied to this tribute in some way.
Check out all of the screens at Wowhead.com.