Google "personality rights", this is trickier than you might think. Subtle nods are usually better than outright likenesses.

The first one is from Cataclysm (2010), which is three expansions in. The human models are from day one, in 2004. Technology marches on.

Have you never played the game? All celebrity references are just that: references. Tributes. Check out Harrison Jones and Haris Pilton as examples. They're not intended to be true likenesses of the person; they're intended to be a nod to them.