Your problem roots from your settings. Somewhere you have a bgcolor on your tables. My hack is displaying correctly. The problem is that the table that displays the forum name, and decription (which is right on top of the table you added the bg image to) has a background color of #000000 (black). The table with the bg color is overlapping the table with the image, but it isn't as wide as the table with the image, so it just displays the corners of the image. All you have to do is take out the the bg color of the table.
