Banksy does all that outdoor stencil art. He started work between 1990-1994, and switched to stencilling in 2000. That his style has become so imitated is a signal to me that what he started was something new, if not in the medium (stencilling isn't new, and nor is graffiti), but in the binding between his medium and his message.
There's a story Banksy tells about discovering stencils as related in his book Wall And Piece and repeated in this article:
I spent one night trying to paint LATE AGAIN in big silver bubble letters on the side of a passenger train. British Transport Police showed up and I got ripped to shreds running away through a thorny bush. The rest of my mates made it to the car and disappeared so I spent over an hour hidden under a dumper truck with engine oil leaking all over me.
As I lay there listening to the cops on the tracks, I realised I had to cut my painting time in half or give up altogether. I was staring straight up at the stencilled plate on the bottom of a fuel tank when I realised I could just copy that style and make each letter 3ft high.
I got home at last and crawled into bed next to my girlfriend. I told her I'd had an epiphany that night and she told me to stop taking that drug 'cos it's bad for your heart.
In Scott McCloud's Understanding Comics - which is excellent, go read it - McCloud puts forward a theory of artistic creation consisting of six steps, steps he likens to an apple. Surface is the skin. Idea/Purpose is the core.
The impulses, the ideas, the emotions, the philosophies, the purposes of the work... the work's 'content'.
The form it will take... will it be a book? A chalk drawing? A chair? A song? A sculpture? A pot holder? A comic book?
The 'school' of art, the vocabulary of styles or gestures or subject matter, the genre that the work belongs to... maybe a genre of its own.
Putting it all together... what to include, what to leave out... how to arrange, how to compose the work.
Constructing the work, applying skills, practical knowledge, invention, problem-solving, getting the 'job' done.
Production values, finishing, the aspects most apparent on first superficial exposure to the work.
(cf. Duffy/Brand's shearing layers of change, for buildings: site; structure; skin; services; space plan; stuff.)
In the subsequent pages McCloud tells the story of an artist learning by starting at step 6, and working their way back - with effort - to step 3. Beyond step 3, there is a choice:
does the artist want to say something about life through his art or does he want to say something about art itself. Choosing the second route, step 2, the artist becomes an "explorer." Choosing the first, step 1, the artist uses art as a tool.
Banksy, I think, invented at step 3. The proof is in the train epiphany anecdote: the story he wanted to tell forced him to do something different. Stencils leapt from somewhere else into graffiti, and the electric arc went via the kite-in-the-thunderstorm of Banksy's eyes. Subsequent stencil artists may or may not have better structure, craft or surface, but they didn't invent at step 3.
I'm not going make a judgement whether doing what Banksy did is "better" or not. I don't believe which steps an artist (or creator) operate in has much relation to "better" or value. But maybe the six steps are one way into to talking about all of this stuff. The breakdown provokes interesting questions: when and where should invention occur, in multiple places or one at a time; what is the interaction between invention and culture and time; how these steps would look when distributed across an organisation including all kinds of people.