Street art, graffiti art, post-graffiti, neo-graffiti, guerrilla art - I'm not really sure if these terms are completely synonymous or if there are subtle distinctions, but I've seen all of these terms applied to Banksy. Banksy is an unknown artist (or maybe a group? I've seen lots of different theories) whose work first appeared in Bristol in the 90's and has since been found in public places around the world. Of course, many of these works have been recreated in LEGO form. One famous work, Flower Thrower, first appeared in Palestinian Jersualem in 2003.
Here's a version by Greg 50.
And another by Jeff Friesen. BTW, follow that link for a great number of LEGO Banksy renditions, and he also has a book coming out later this year.
Two more by Alex Eylar and Klyph R'ha Ben Sun.
Here is the original.