See my update below, Google basically pulled the background images.
At midnight of June 10th, Google flipped the home page of Google.com to automatically show a background image. They announced that this will only be automatic for June 10th, a 24 hour period.
Lots of people are calling it a Bing impersonation, which I assume Google knew and decided they didn't care about.
But at the same time, although I personally like Google really pushing people into the customized home page - I think they should have given an opt out. I think most people had no clue that this was an option until Google went this drastic route, but give them a way to opt out.
I was browsing the Google Web Search Help forums and the first 6 pages of threads in that forum, as of 8am (EST) are all complaints. Here are the first 3 pages, I ran out of room...
Google, when doing something this drastic, next time, just put an option to go back.
Update: Google removes background images early and adds a link explaining things. Google's Marissa Mayer tweeted they just removed it. But she did not explain why. I assume it has to do with the complaints.
Google updated their blog post saying:
Update June 10, 11:31AM: Last week, we launched the ability to set an image of users' choosing as the background for the Google homepage. Today, we ran a special "doodle" that showcased this functionality by featuring a series of images as the background for our homepage. We had planned to run an explanation of the showcase alongside it-in the form of a link on our homepage. Due to a bug, the explanatory link did not appear for most users. As a result, many people thought we had permanently changed our homepage, so we decided to stop today's series early. We appreciate your feedback and patience as we experiment and iterate.