scrap mural

Maybe "décollage" is the term, though to be accurately applied it may require the art be intentional rather than accidental or discovered. More: https://www.tate.org.uk/art... and https://www.nationalgalleries.org/art-and-...

Perhaps only specific to certain artists, but also known as "affiches lacérées," such as here https://www.maxhetzler.com/exhibiti... and here https://www.galerie-vallois.com/edition...

Also sometimes called "urban palimpsest," though art so described is far more intentional, at least according to what I am seeing: https://kagi.com/images... (and, ugh, just realized that the word "intentional" is now skunked by AI overuse).

Gonna have to start using "purposely" or "purposefully" instead of "intentional."

@grantbarrett ooooh thanks for the references!