Facebook has its default log in page background image,but You can also replace it any image which you want.Follow given below steps.
1).
Click on this link. in Google chrome.
2).
Install this Extension.To install extension click on
"extension" in the list given at left side below
"utilities".
3).
When you click on extension different images will appear.
4).
Move cursor on any image.Below any image click on "+ Add to
chrome".
5).
Your required extension will automatically installed and will open
on your browser in new tab.
6).
Log out from facebook if you are login already.
7).
Open www.facebook.com.
8).
You will see a new colour full log in page.
Note:This trick will only work if you have google chrome browser.
