Well, let me make that suggestion then. I would like to remove all pictures for which:
- no author or source is known, and
- there is no good reason to believe they are public domain
From my own sample, which unfortunately did not get posted on the list yet (I sent it from another email address, and it is waiting moderator approval because it is from a non-subscribed address), I think that this might include as many as 20% of our current images.
If so, then I'm wrong and will immediately change my position. If 20% of our images are from questionable sources, we are in a bad position and need to correct it quickly. Given the large number of images that have no provenance information, perhaps we should rearrange the image-upload process to require uploaders to click through a "where did you get this image" page before they enter the file name. Of course that won't force anyone to enter anything, but it will make it more obvious that they should.