Unfortunately, you could change the desktop and the Lock screen wallpapers, but you couldn't change or disable the sign-in screen image. This complaint is one of the reasons why we have themes and the ability to change wallpapers. The wallpaper was well received, and it was also featured in the desktop, but after some time everyone will just get tired of looking at the same image again and again.
When the operating system released back on July 29, the sign-in screen featured the default background Microsoft created featuring the Windows logo made out of light. In this preview, Microsoft is rolling to Windows Insiders improvements to the Lock screen. You can view how this feature in action and some of the other changes in our hands-on video highlighting the most important features on Widows 10 build 10547.
