You mean to put an image in the background of the folders without modifying the explorerframe.dll?, If so, don't know a possible way to do so.
Well, not exactly. What I was actually hoping for was the ability to create a set of 'GradientFill1' and 'GradientFill2' properties for it instead of just 'Fillcolor' to have it use a 2 color gradient rather than just a solid color without having to use any image at all (this would allow me to use a gradient without having to use any pics, thus avoiding manually hacking explorerframe.dll).