This is a positive move for the community. Thank you for clarifying the guidelines. There are several works posted that have no clear proof they are the original content creators. I have reported some of the plagiarists but most art are difficult to trace.

This is a common method some authors use to fake the art.
here this helps the plagiarism escape from detection. They don't credit their sources, or even show process shots that the work belongs to them.

Also, there is a method where one can just take a photo of someone else's painting without giving credit to the artist that painted it.