Wallpaper does get restored after a LogMeIn Rescue session I recently hosted a remote desktop session with a HP tech support who used LogMeIn Rescue for the remote screen share and control session.

As part of the session, LogMeIn Rescue removes the desktop wallpaper, so that it doesn't add complexity/bandwidth to screen share stream.

Usually the desktop wallpaper gets restored after the remote session is concluded. But this time it got restored only on my MacBook's built in screen and not on the connected external display (connected via HDMI via a Thunderbolt adaptor).

I've shut down and restarted my computer, but to no avail. Any ideas? I am using a 2017 MacBook Pro running macOS Mojave 10.14.x.
Have you tried going to System Preferences->Desktop &amp; Screen Saver, then re-select your preferred wall paper on your secondary desktop?
LogMeIn recommends turning off the option to remove wallpaper if this keeps happening by going into the Preferences, General Settings, and uncheck the option for "Disable wallpaper and user effects on host computer", then click Ok.