"You can remove your background image at any time by clicking Remove background image in the bottom left corner of the homepage."
But that just reverts it the default image, not the old white.
Edit: Actually it looks like the forced background is just temporary, for 24 hours, according to the Google Blog post: http://googleblog.blogspot.com/2010/06/art-of-homepage.html
http://www.google.com/pacman/
Guess someone was listening!
"You can remove your background image at any time by clicking Remove background image in the bottom left corner of the homepage."
But that just reverts it the default image, not the old white.
Edit: Actually it looks like the forced background is just temporary, for 24 hours, according to the Google Blog post: http://googleblog.blogspot.com/2010/06/art-of-homepage.html