I have my forum widths fixed and centered like his... now I have an image I would like to use as a repeating background (see attached image) How do I do this in the ACP?
Appearance -> Style properties -> General -> Background (options have image, add the url there and set the repeat as you wish)
That would change the background, if you want the same bg for the logo strip as well
Appearance -> Style properties -> Header and Navigation -> (again, option to add an image is there).
That's how I added a image to the background, maybe there is a css to change it all together at once but I'm not aware of that