Recently, I've reinstalled Windows on my laptop, upgrading it from Windows 7 to Windows 8.1. Now, I want to change the theme (or at least, wallpaper) which is shown on the screen before any user logs in. (Note: not the user lock screen, but the one which appears upon clean reboot - systemwide)
I don't want it to be a custom image, just another one from standard. Is there a way to do it without group policy or much tinkering with the registry? I've used one of the tricks to move User folder from system SSD drive to secondary HDD on the PC, and the result was that I couldn't upgrade to Windows 8.1. So I want to know if there is any more-or-less native way.
NOTE: this is not a duplicate of the question shown below, because my question refers to systemwide locking screen and not the user custom one. As you may guess, there's only one systemwide image per computer, but multiple user custom ones.