Scroll down and browse around for the background that suites your shop. If you like one then all you have to do is highlight the code (ctrl+a) that you need, then copy (ctrl+c), then paste (ctrl+v) on your user preferences (found in help) or your shop (create/edit). Please note that the backgrounds may not look the same as the images below because I had to shrink some of them so they would fit the page.
