Windows 10 lets you customize the look of the lock screen with personalized pictures within the Settings app. It also remembers the last five images you used. If you don’t like any of the default images in the history—or want a fresh start—you can remove them from the suggested images.
Your lock screen history in the Settings app shows five images that Windows picks randomly from a hidden folder on your system. These images include any that you’ve previously used as a lock screen background.
By default, Windows shows the five most recently used images, so you could add new images to push out old ones from the suggestions. The trouble is that those images still exist in the folder of lock screen images and sometimes Windows will get mixed up and not just show the most recent images.
There is a way to remove these images. You will have to jump through a couple of hoops, though.
The first hoop involves finding the right folder. Windows stores all these images in the following location:
C:\ProgramData\Microsoft\Windows\SystemData\User_Account_Security_Identifier\ReadOnly
The User_Account_Security_Identifier part of that path is different for everyone. Each user account on the computer has a different Security Identifier (SID). To find yours, fire up the Command Prompt or PowerShell and type the following command at the prompt:
whoami /user
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Source: How-To Geek
