Open notepad and copy the following code :

[{BE098140-A513-11D0-A3A4-00C04FD706EC}]
iconarea_image=D:\modernhackerss.blogspot.com\backgroundimage.jpg
iconarea_text=0x00FFFFFF


Here, the path in the 2nd line of code represents the path of your picture. so just change at dere only....

 Now save this file as DESKTOP.INI in the location(any drive or any folder) where you desire to set the background picture.
 After setting it in your favourite location,close the drive and open the location again.
DONE !! .. your picture has been set as background picture for your desired location.