2012 Macbok pro display issue
What is the solution for the display issue as shown in the picture attached
First try a SMC reset, do it two or three times:
How to reset the System Management Controller (SMC) on your Mac - Apple Support
If that does not work:
In Finder go to StartupDisk->Library->Caches
locate the file “com.apple.desktop.admin.png” and move it to the desktop
then restart the mac.
If the issue is gone, delete the png from the desktop.
If not gone, it may may be an issue with the hardware.