the image URL which you wish to display there, if the image is right on your web server you could just put it's name (ie "myimage.gif"). You could also put a full URL to the images you want to display (ie "http://www.myserver.com/myimage.gif").
-Spy
Power - The only narcotic controlled by the SEC, not the FDA.
make more, use an image editing application to create any image you want and than upload it to your webserver. You'll probably want to try a few differant image types before you come up with something you like enough to stick with.
Just keep in mind that when you hit the end of the image it will repeat (that's why gradients tend to work well).
-Spy
Power - The only narcotic controlled by the SEC, not the FDA.