Steir on the Street? Shot on 21st Street, outside Eyebeam Gallery
Same location, different reference
A few Pollockian drips on 20th Street
Rothko on a dumpster?
These images were taken over the course of several months, so they may not be there now.
Update, August 3: In his blog, In it for Life, Tim McFarlane shows a fabulous "Rothko Wall" in Philly.