How to change the login screen background picture on macOS 10.15 Catalina. Changing the login image on 10.15 requires the use of terminal and is considered an advanced process. Please be careful!
Copiable Terminal Code Here (at the bottom of the guide):
A restart should reenable System Integrity Protection (SIP) but you can also reenable manually by rebooting to recovery mode again (Command + R on restart) and use the terminal command “csrutil enable” without quotes. You can check if SIP is enabled by using the terminal code “csrutil status” without quotes.
Published by Anson Alexander from http://AnsonAlex.com .