When you open "www.google.com", you just see simple back ground. You can put your own picture or any your favourit picture on google page as background.
For this purpose create your gmail account and add your pictures on facebook or google + account. Now open google.com. click on the link lower side of the page "change background image"
Now on the next message box you can select image from the google gallery but if you want to put your own image, then click on the "your picasa web photos". You will see the list of pictures you have added on facebook or google +. your image must be at least 800 x 600 pixels in size.Click on image and and then click on select button.
Now open "google.com" page. You will see your selected image as a background. After signing out you can't see this image.
