Here’s a great site, it’s been around for a while but I forgot about it…. http://otherthings.com/grafarc/flash/view.htm
The author documents walls of graffiti and how they change over time, it’s great. It shows the changing of the environment by human agency and is therefore archaeology (cf. http://www.archaeology.blogspot.com/2003_12_01_archaeology_archive.html#107255655726655576 ) .
But who cares, it’s quite pretty too!