On both our 2019 MacBook Pro & MacBook Air running OS Monterey 12.1, the default Screen Saver pictures have disappeared.
When I select Origami or Shifting Tiles, only colours appear on the screen. On the right hand side of the screen in the box "Source" only "Colours" is displayed.
Any suggestions please as to how can I retrieve the pictures.
They used to be in /System/Library/Screen Savers/Default Collections, so if you have a pre-Monterey backup then you could recover the images from there, copy them somewhere else, and use the 'Choose Folder...' option in the 'Source' list to point the screen saver at your copy.
(In Monterey that folder contains only a single '4 - Colors' subdirectory.)