This isn't actually a mod in WoW. It's built in. I suspect that this is in the works for EQ2. If you want to know when, I'd have to say
Soon™.
From
Game Update #27: Sept 6, 2006
*** User Interface ***
- The character portrait in the inventory window now has a plain background and no longer follows the animations that your character makes in the game world. You can use your mouse to rotate your character around. Why make such a change? We're keeping that under the cloak of secrecy for now...