Change Log On Background (Mac)

At first the storage location of the default background has to be detected. Once found the file should get replaced by another picture. Optionally, image properties of the new picture could get adjusted to the default picture.
1 answer

Change Log On Background (Mac)

The default background of the log on screen can be found under
/System/ Library/CoreServices and file is named "DefaultDesktop.JPG".

Before replacing this file by another, it's nice to have a copy stored somewhere else (in case of restore is required).
Image properties of the new picture should be 2560 × 1600 pixel with a resolution of 72 pixel per inch (for Mac Book 13,3''). (optional)
Afterwards the new picture is renamed into "DefaultDesktop.JPG". Go to the directory /System/ Library/CoreServices and overwrite the old default background with the new picture.
Change can be seen after reboot.