Can I use a picture or texture for my html background?

Hi all,

My player template has a gray background color. I know I can modify this by changing the color scheme, but I'm wondering if there is a way to use a patterned background instead, or a picture?? I'm guessing not, because I couldn't find the option in the template or color scheme editor. But maybe there's a way to do it by modifying the published output somehow? Any one tried that? Here's a screenshot of one of the courses in the community showcase, with the area I'm talking about. Thanks in advance for any ideas!!