Windows 10 Professional - Local policy setting for default Lock Screen - Microsoft Community 


a. Press Windows + R keys together, type gpedit.msc in run window and press Enter.


b. In local group policy editor, under computer configuration, click to expand administrative templates.


c. Expand control panel and then click personalization.


d. Right click "Force a specific default lock screen image" and click edit.


e. Select enabled, click apply and then click ok.


f. Similarly, Right click "Force a specific Start background" and click edit.


g. Select enabled, click apply and then click ok.