Setting Screensaver, Lock Screen, and FileVault screen to same image (Mojave)

[Eric84]

My company is currently interested in modifying multiple settings on the Mac clients to a specific .jpg or .png. The idea is the have some sort of safety message in an image and lock it in for their ScreenSaver, Lock Screen background, and FileVault background so that it is visible often. Note that we do not want to change the user's actual desktop wallpaper and we allow them to choose their own wallpaper.

Given the direction and a desire to update the "safety message" every few weeks, I would assume a Configuration Profile would be utilized in order to lock it down but cannot seem to find the solution that would allow me to modify these 3 areas only. Any help or tips is greatly appreciated. Thanks in advance.

[bradtchapman]

So ... they want to put the safety message in the wallpaper. Make sure they know that at the initial login window, and with FileVault2, the wallpaper is blurred.

The default wallpaper is linked from two places

/System/Library/CoreServices/DefaultBackground.jpg –> /Library/Desktop Pictures/Mojave Day.jpeg
/System/Library/CoreServices/DefaultDesktop.heic –> /Library/Desktop Pictures/Mojave.heic

Rename the original files in /Library/Desktop Pictures and save your new 'default' image as 'Mojave.heic' (use Preview to export an HEIC file). You'll need to distribute this as a package, not a configuration profile. As you update the wallpaper, replace your package and flush the policy log.

The alternative is a 'policy banner' that appears at first login where users have to click OK to continue. I personally find them annoying AF, but some one in your org will probably LOVE it.

Apple: How to set up policy banners in macOS