Hi there
How can I answer files 
I change the background image of the operating system.
Wallpaper of the address of the image file you?

Sorry my English is poor :(

Hi Saeed,

Are you going to make a answer file to set the background of the system or just want to know the address of the Wallpaper ?

If it is the former ,we can refer to these links:
SystemDefaultBackgroundColor
https://technet.microsoft.com/en-us/library/jj570859.aspx?f=255&MSPPError=-2147217396
Custom Windows 8.1 Image Part 2
http://ammarhasayen.com/2014/01/31/custom-windows-8-1-image-part-2/

If that is the latter:
The Login Screen Wallpaper is stored at (before you log on)
C:\Windows\System32\oobe\background.bmp

Desktop Wallpapers are stored at (after you have logged on)
C:\Windows\Web\Wallpaper\

NOTE: This response contains a reference to a third party World Wide Web site. Microsoft is providing this information as a convenience to you. Microsoft does not control these sites and has not tested any software or information found on these sites.

Best r