I COULD HARDLY BELIEVE MY EYES WHEN i FIRST SAW THESE. These pictures were actually drawn only using artisits brushes and plain old dirty windows.
The only problem is that after all of that work, a good rainstorm could wash it away. I guess that's why the guy took pictures. This technique is called reverse graffiti, and apparently is being used by advertisers in Europe. The artist who did these pictures is Scott Wade and you can see these pictures and more at www.environmentalgraffiti.com.