This method will allow you to put a custom background to your folders.
The trick is to make your folder a system folder and then you are done with it.
Just fire open the notepad and copy paste the following code into it.
iconArea_image=<"The name and location of the wallpaper">
save the file as "desktop.ini" in the folder that you want the wallpaper in.
Refresh and voila.....you are done.
The image will be tiled and you may not like it......
so just choose the image that matches the current resolution of your screen.
This is what I did.. to my counter strike folder.
Image resolution was 1024 x 768 and my resolution was 1280 x 1024
So I increased the image size using photoshop(you may use paint) to the next permitted level and this was it.