Copy this crap to your desktop.ini file inside the folder you want to add teh background to, you have to use the address bar to get to it, it's hidden. And, yes, the 'teh' is intentionial, j00 fūl!
--------------start copying after this line, young padawon---------------
[.ShellClassInfo]
IconFile=put your icon dealie here, look below
IconIndex=0

[{BE098140-A513-11D0-A3A4-00C04FD706EC}]
IconArea_Image=put the path to your image here if it is in this folder or any of it's subfolders go like this:  'gabuin.bmp' or  'subfolder\gabuin.bmp' no 's though. and it doesn't have to be a bmp.