I have the code on my tester and do believe the problem lies with use of "HTML" "BODY" and "BACKGROUND" element. In a sense, you're coder is attempting to use the entire page for worksheet rather than the Description section and only that frame (the limits of the template).
My suggestion would be to use CSS Code inline STYLE on a new (whole section) table and attribute "background-image" for the background of just the table. I'm getting it to work on my tester, but not the practice board. Give me a few more minutes and I'll either get it fixed or give it back with at least my best attempt to fix.