2 Answers

Instructions
1
Open a Web browser on your computer and go to Google.com.

2
Click the "Change Background image" link in the lower-left corner of the Google homepage.

3
Log in to your Google account by entering the email address associated with your Google account and your password and clicking the "Sign In" button.

4
Click the "Change Background Image" link.

5
Select the background image you want to use for your Google homepage. You can use images from your computer or you can search for images in Google's library.

6
Click the "Select" button to save your selection and change the background image for your Google homepage.

Read more: How to Change Your Google Homepage Background | eHow.com http://www.ehow.com/how_7731606_change-google-homepage-background.html#ixzz230eJw52t

 Go here if you are talking about google chrome...

https://chrome.google.com/webstore/category/themes?utm_source=chrome-ntp-icon