Google's spring, summer, autumn and winter cleaning has left quite a few annoyed users. While most of the things Google kills off aren't all that popular, some are loved by plenty of people.
Case in point is the homepage background image. The feature was introduced to great fanfare a couple of years ago.
But it seems Google was not seeing the usage numbers it had hoped, not enough to make it worth the trouble of updating the feature every time the Google homepage changed, so it dropped it. As of November 16th, all background images have been removed.
Plenty of people loved the feature though and have been looking at alternatives. If you're using Chrome, there are a couple of good alternatives in the Web Store.
Background Image for Google Homepage, for example, makes it possible to add any image online as a background for your Google homepage. All you have to do is provide a link. You can also search Flickr or pick from the built-in images that come with the extension.
Custom Google Background is a bit less user friendly, but it comes with several customization options besides just picking a background image, like the option to remove the Google logo altogether.