Make the overview background a blured darkened version of the user defined background and use blured grey panels to represent differnet workspaces.

The current Gnome 40 design can be seen below.

The main advantage of this design is that users can easily grasp how workspaces work as each workspace is represented as a standalone desktop.

However, this introduces an ugly black Overview background.

To solve this, make the overview background a blurred darkened version of the user-defined background and use blurred grey panels to represent different workspaces.

Or a combination of both designs could be applied as seen below. Made with GIMP

This way, we can see a beautiful desktop and easily grasp how workspaces work.