Graffiti / Street Art

Graffiti is not a new thing like the bold letters on the side of bridges, designs of this nature have been around for thousands of years by way of prehistoric cave paintings. There were some Drawings and paintings on cave walls from the Paleolithic period (17, 300 years old) discovered in 1940 by some teenagers. These paintings depict everyday life such as hunting. 

These are obviously not as complex as some of the intricate designs that there are today but it shows us that the want to record experiences and thoughts so your experience can be passed on. Not so much today but here was where it all started.
        Graffiti also also popped up in roman history with markings made on the walls in the ancient city of Pompey. The romans carved what appears to be small human figures and some latin scrawled over the top.

Killroy/Mr. Chad was a worldwide graffiti phenomenon of which no
one is sure of the exact origin

Graffiti is everywhere but we only think of graffiti as the sprayed paint on the concrete walls. Graffiti is in adverts. The Vauxhall corsa with the moving graffiti on the walls which follow the car. The graffiti is obviously not actually painted but even technology which doesn't use paint is inspired by wall art.