I never received any message...
You will run into issues trying to develop a flash based template, but I know some that have succeeded long ago. Just don't try to do flash upload unless you intend to allow an unprotected folder in the root (some issue that stopped us from enabling mass upload with flash). I wouldn't bother though honestly. Flash just breaks your usability and accessibility, it's better for small objects.
What you ask is tricky CSS wise, there isn't a real easy way to explain it unfortunately, and multiple ways you could possibly try to do it. That positioning you have at the moment only really works for the body background element, and this is also the cause of your scrollbar problem, unless you accommodated for that with some padding on the left/right of the body itself, then remove the max/min-width on the inner elements (change it to a fixed width of about 960px) so it holds a steady width. Then.. with the bg image you would want it to be the same width of the total minimum width of the page content... that might work. Template is fairly kawaii now lol.
