Steps to change Windows 8 logon screen within the OS
1. Open the Control Panel by clicking on the Control Panel tile on the Start Screen.
2. Next, A control panel Window opens. Click on the Personalize.
3. Next, You will see the list of default images available in Windows 8. Click on the images to use it. If you want to use your own image then click on the Browse button.
4. If you have clicked Browse then on next window you will find an option to choose your images. Click on the Files tab. Navigate to the drive where you have saved your images.
5. Next, you will see your image. Click on it and that will be used. Press Windows + L hotkey to view the new lock screen background. That are the complete steps to change Windows 8 logon screen.