There are 2 ways to do backrounds in tourneys.
You can either use the backround image box and place the
url inside the box, and submit it and for those that dont know what a url
is the address to the pic or backround you use it will have a tag of 
http:// in front, otherwise known as a link.

Or

You can use the HTML codes and put it in the Customize Html box on the page:

<*body STYLE="background-image: url(URL address HERE)">

You put the url to the image in between the ( ) in the code, and you also
have to remove the * at the beginning so it will work for you. 

If you want your backround to remain still and just have the pictures move 
over top of the backround, you are gonna place this code in the box, 

<*body bgproperties="fixed">

once again you are gonna have to take out the * at the beginning so it will work