You need to add the following key in the registry:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionAuthenticationLogonUIBackground]
“OEMBackground”=dword:00000001

You can save it as a .reg key and it will add it to the registry.

or download the txt file and use it as the registry file:    background.reg

Next step is to add the background image named:  backgroundDefault.jpg

to the following directory:

C:WindowsSystem32oobeinfoackgrounds  (You may have to create the last 2 directories)

That’s all folks.

If this helped you, erectile  consider buying me coffee!    Thanks!