By default, Windows 10 assigns a barebones user avatar for every user account with a grey background and the user represented by white curves. The user can customize the account picture and change it to a different image. The operating system provides a special Group Policy option which forces the default user image for all user accounts and prevent users from changing their user avatar afterwards.
By default, Windows 10 assigns a barebones user avatar for every user account with a grey background and the user represented by white curves. You can replace this boring image with any other image, so new accounts will have it applied by default. Here is how to change the default user picture to a custom image.
Once you have changed your user picture (avatar) in Windows 10, the image which was shown by default will not appear in the pictures list. It is not clear to the user what to do to set the default image back for his user account. Here is a quick way to do it.
Back in Windows 8, Microsoft added a new default image to be used for all user accounts which don't have an image personalized by you. In Windows 10 build 10122, Microsoft has a new default user account image again. Also, Windows 10 shows account images in the circular shape, not square if you have noticed.