I enjoy looking at graffiti aka street art. Some works are utterly stunning. I know that some are done without the owners permission. Though often the art looks much better than a dull grey wall.
Vandal art?
The Vandals were a large East Germanic tribe or group of tribes that first appear in history inhabiting present-day southern Poland. Some later moved in large numbers, including most notably the group which successively established kingdoms in the Iberian Peninsula and then North Africa in the 5th century