Go to Home---->Account---->Styles & Themes
For example, you are using the Standard Theme, click on 'copy'.
In the Edit Theme Page, scroll down to the 'Page Background' setting and click on the dropdown arrow for 'Custom Background' and choose 'Yes'.
This will open up a new option for 'Background Image' you can upload by clicking on 'Choose File'.
Or you can browse all of the themes other members have created and choose one to use 
how do i make my backround difrent on my home page
iv been wondering just please help