How do I set a unique wallpaper for each GNOME workspace?
Search and install "Extension Manager" from Ubuntu Software.
Press the Super key to open the overview, search and open the tool you just installed.
When it opens, go to the “Browse” tab, find and install the “Walkpaper2” extension.
Go back to the “Installed” tab, click on the gear icon for the extension. In the pop-up window, simply click on the image above to open the dialog box to set a new wallpaper.
GNOME by default has 2 desktops and is added more dynamically. To set a fixed number of desktop workspaces, go to “Settings -> Multitasking -> Workspaces”.