[theme: Clean Retina] hiding header/footer pattern

Hi all,

I want to add a background image to this theme and hide the header and footer pattern. In ‘theme options’ under ‘custom background’ it states “Note: The custom background change will be reflected in content part not the header and footer part. If you want to reflect change in the footer and header part as well, please add your custom css from below to hide the header and footer pattern. You will then see the changes in header and footer as well.” What custom css will accomplish this? Also, if I just wanted to replace the existing header pattern with something new, what css would I use?
Here’s a link to the site which is still under construction:

shawnjomalley.com

Thanks.

Dennis