"An idiot's guide to art made by idiots"
Pictures of walls is an online photo gallery comprised of anonymous submissions of amateur graffiti. The site's name is a nominal term. There are also pictures of sidewalks, billboards, bridges, manipulated objects, etc. There is no readily apparent contact information, and no legal statements or copyright claims on any pages, and the identity of the site admin and domain owner are unclear.
It's a ponderous, sentimental, self-sustained counter-culturistic bohemian playground of the internet. But don't take my word for it, peruse for yourself. It's highly addictive, and should probably be avoided unless one is feeling particularly unproductive.
There is writing on the wall.