I contacted the designer about my little background problem, but was not able to resolve the issue. Poor Critical Mass was homely as a mud fence all. day. long.
Super Dad to the rescue! He studied on it for the afternoon and had the solution waiting for me when I got home.
Turns out, the URL provided by My Cute Graphics wasn't the actual URL of the background graphic. He rummaged around the in the source code and found the real URL. My hero!