windows 8.1 personalization question!!

[Tourage]

So guys, I just reinstalled my windows 8.1 but there is one background screen that I can't find where to change it.

The background screen I'm talking is the Login Screen, press Ctrl + L to go to lock screen and click on it so the Login Screen can appear, mine just has a solid color as background, does anybody know how to change it to a picture?

 

[USAFRet]

http://windows.microsoft.com/en-us/windows-8/desktop-background-lock-screen

 

[Tourage]

http://windows.microsoft.com/en-us/windows-8/desktop-background-lock-screen

yeah, that link has just the desktop,start and lockscreen. The picture I want to change is the login screen picture