You can use the built-in template in UEM. Go to the Personalization tab and create a new config file, Use a Windows Common Setting template, Wallpaper - AppData not redirected.
It contains the following settings:
# This Flex config file references the built-in "Wallpaper - AppData NOT redirected"
# Windows Common Setting.
# It has been configured to be 'OS-specific' (on the Advanced tab).
# Wallpaper settings will be imported at logon and exported at logoff.
# IMPORTANT: This Flex config file assumes that you have NOT redirected the AppData folder.
# If you have redirected AppData, disable or delete this Flex config file and create a new
# Flex config file selecting the "Wallpaper - AppData redirected" Windows Common Setting.
#
# Expanded settings for Windows Common Setting 'Wallpaper':
#
[IncludeRegistryTrees]
HKCU\Control Panel\Personalization\Desktop Slideshow
HKCU\Software\Microsoft\Windows\CurrentVersion\ThemeManager
HKCU\Software\Microsoft\Windows\CurrentVersion\Themes
[IncludeIndividualRegistryValues]
HKCU\Control Panel\Colors\Background
HKCU\Control Panel\Desktop\TileWallpaper
HKCU\Control Panel\Desktop\TranscodedImageCache
HKCU\Control Panel\Desktop\TranscodedImageCache_000
HKCU\Control Panel\Desktop\TranscodedImageCount
HKCU\Control Panel\Desktop\Wallpaper
HKCU\Control Panel\Desktop\WallpaperStyle
[IncludeFiles]
<AppData>\Microsoft\Windows\Themes\slideshow.ini
<AppData>\Microsoft\Windows\Themes\Transcoded_000
<AppData>\Microsoft\Windows\Themes\TranscodedWallpaper
<AppData>\Microsoft\Windows\Themes\transcodedwallpaper.jpg
<LocalAppData>\Microsoft\Wallpaper1.bmp
\\ Ivan
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