[JamesC70]

Do you really need the header background to be different from the rest of the page (navigation bar and below)?

I imagine the whole page to be like looking outside. From top down I see clouds and blue sky (header), treetops (background around navigation area), trees (notification area), and then grass (actual page content).

Using this method, I simply create a background image that wraps across (left to right) and then graduate to a solid color at the bottom (below the grass would be green background color).

I upload the background image to my server, then set it here:
AdminCP -> Style Manager -> (select theme) -> Body -> Standard CSS Attributes -> Background

Use CSS to specify your options in this field:
#000000 url(http://yoursite.com/path/to/image/background.png) repeat-x would have a solid black background (#000000) underneath the background image. repeat-x tells it to loop across, but not down.... add repeat-y for a tile effect.

If this method doesn't work for you (maybe you bought a theme from someone? header_background is not vBulletin 3.x default), then scroll down to Additional CSS Defintions to see if it's defined there. :up: