Making background image fixed in Elegant Grunge template

Hello

I am using the elegant grunge template for my website and the only lingering formatting issue that I’m having is regarding the background image.

When you adjust the physical size of the browser window, the image on the background adjusts with it, specifically when the browser window is made about 50% thinner than full size. I don’t want the background image to adjust. I want it to remain fixed regardless of browser window size. The elements in the foreground, for example the sidebar elements under which the background should lay, remain fixed in place, but the background slides away from it.

Please let me know if there is additional information that would be helpful for solving this issue.

Thanks for your time!