Creating a wallpaper MDM configuration is a two-step process as the image must exist on the device before the configuration can use it for the wallpaper.
Getting the image onto the device
Initially, the image would have to be placed on the end user's device, this can be achieved by deploying it as a Custom Software where the installation script moves the image to a location of your choice. In this example we are moving and renaming the image from addigy.png to /Library/Addigy/Wallpaper.png:
Note: The move command (mv) can also be used as a renaming command.
Deploying the wallpaper MDM Configuration
Creating the MDM Configuration can be found under Policies -> Catalog -> MDM Configurations -> Add Configuration+ -> macOS -> Restrictions -> Desktop and Finder.
From here the path set previously would be placed in the Desktop Picture Path (/Library/Addigy/Wallpaper.png):
From here you're all set to add and deploy both items to a policy and see your wallpapers change!
If you have an Addigy account and have additional questions, you can create a ticket by emailing support@addigy.com.