Have a different wallpaper on each workspace.
Compile the extension by running
# make all
Install walkpaper.zip
using Tweak Tool and restart GNOME Shell (alt+F2 + 'r')
To set the background image for a workspace, switch to that workspace and use any method to change the background E.g. standard background chooser (e.g. secondary click on background, "Change Background"), then close the backgrounds dialog (otherwise trying to set background on another workspace may trigger a workspace change back to the WS with the dialog)
You can even use another extension or program that changes the backgrounds automatically.
Switch away from the workspace to trigger saving the current background.
You can also manage extensions from https://extensions.gnome.org/local/
This project is licensed under the GNU License - see the LICENSE.md file for details
Based on https://github.com/BlinkBP/walkpaper -- Thanks!