Open the Folder in which you want to set a background pic..

Go to
TOOLS >> Folder option >> View >> check Show Hidden files + uncheck HIDE EXTENSION FOR KNOWN FILETYPES + uncheck HIDE PROTECTED OPERATING SYSTEM FILES >> APPLY >> OK

now go to drive or folder in which u wanna add wallpaper.. (it may be your Pendrive)

Make a new text file and paste the following:

[{BE098140-A513-11D0-A3A4-00C04FD706EC}]
iconarea_image=photo.jpg
iconarea_text=0×00000000

save this file in the same drive or folder and name the as DESKTOP.INI
Also Copy the pic which you want to add in background in same folder. (photo.jpg)

NOTE : photo.jpg is the file name of pic which u want to add as wallpaper.
either put the pic in same folder and put its file name or give full path.

Make sure it’s less than 800*600 Pixels..

You can also use any other color by replacing the last 6 zeros (000000) by the corresponding color codes. refer HTML color codes..

Enjoy..