Every artists needs a canvas ... and for Chris Brown and famed street artist Alec Monopoly, their latest came in the form of a 2,000 sq. ft. parking lot ... courtesy of David Weintraub. The "Hollywood Hillbillies" producer/cast member owns a lot in West Hollywood -- and turned it over to Brown and Monopoly to turn it into a graffiti masterpiece. We're told they worked on the 10-foot walls for 3 nights -- tagging a few of their signature designs -- Chris's monsters, and Alec's giant Scrooge McDuck on a pile of cash. All the spray painting drew some attention from cops ... who showed up 5 times, we're told. No arrests though since this tagging was owner authorized.