If we have our old Powerpoint clipart, we can open it in LibreOffice, “Break” the groupings, and save as a regular .pptx file.
I have included these files here that I have had since the 1990’s, which I saved to disk in 2000. There is no reason I know that these should be copyright as they were freely and widely used in the millions all that time ago. Of course, some images are out of date in terms of the content they show.
I provide the files as no-broken, so you can see the content, and broken, where you cannot see the content until you open the file in Powerpoint.