When I was at art school, two of my colleagues found a wall from a
demolished building on some wasteland out of town that would have made
an excellent canvas for a mural they were planning. But it was covered
in graffiti. Real graffiti by kids with spraycans, not
destined-for-publication graphic designer posturing. To make their
mural they would have had to destroy it.
One of them later acknowledged to me that they’d done the right thing by not doing so.