Different wallpaper for each workspace.
Feature summary
GNOME 40 Shell should allow to set different wallpaper for each workspace or set random wallpaper automatically.
How would you like it to work
I'm not a developer but I would suggest that, by clicking on 'Change Background...' option in right click menu, it may open a dialogue similar to that of 'Select Network' or something like file picker to select background for that workspace. A random background for each workspace may also be set automatically for each new workspace. There might also be an option in settings app to set a certain wallpaper according to the category for which the workspace was created (like work, gaming, entertainment etc). This is just my idea, and i think that the implementation can be much better than this. I also think that this behavior very much suits the design of GNOME 40. Instead of seeing same picture above the App Picker, different pictures will look distinct and cool.