The current avatar (very nicely supplied by Jared) is from a photo in "The Making of ROTS" book. ILM had sent the Episode I Yoda puppet to Shepperton Studios in England for eye-line use during the ROTS reshoots. When the Yoda puppet was removed from his packing materials, he had this demented look on his face due to the breakdown of the silicon materials. Here's the excerpt from the book (available at all fine booksellers near you):
Because of budget constraints, the Jedi Council chamber is being shot in sections. The first group of five chairs is placed on their marks and Yoda is unwrapped-to reveal a truly deranged version of himself-which will be used only for camera reference and eye lines.
"Have you seen Yoda's expression?" Knoll asks Lucas. "It's priceless."
"Somebody has to get a photo of that," Lucas agrees, and Knoll adds, "Something's definitely wrong with the universe."
The thing that makes the photo even funnier is the look on Sam Jackson's face. Yoda is sitting in a chair, and there's Sam in full Mace Windu regalia next to him, giving him this "WTF?" look out of the corner of his eye.
Short version, Yoda looked so demented it made me laugh like I was demented. Hence my selection of the avatar.
