Even when the PC is locked, you can use voice commands via Cortana to play music, set reminders, or ask questions. (Note: This feature is less emphasized in newer Windows 11 builds but remains available for those who enable it).
Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Personalization and create LockScreenImage (string) with the path to your desired image. Use with caution; incorrect edits can disrupt system behavior. lock screen background windows 11