[tbworld]

I am not the expert in this area, graphics are not my thing, but I believe you either need to go to a fixed vbulletin layout or use a column on the left and the right, instead of a fixed graphic. This method would also cut down on the image size as @Max Taxable has already indicated. There are threads here on vBulletin.org on how to setup the HTML. (They might be a bit difficult to find.) If you cannot find the threads, look at a few sites and examine the source HTML -- that should give you the presentation logic that you need.

You might try searching for the term "graphical borders", "graphic border".