I just discovered the work of Alexandre Farto aka VHILS - a Portuguese street artist. His projects appear on all sorts of surfaces ( see 1, 2, 3, 4) but what really blew me away is his work on street walls. Some of his murals are simply hauntingly beautiful. For example see these murals in Italy:

Or this work from Shanghai depicting the face of an evicted tenant  on a building slated for demolition (via a Shanghaiist story):

I am now wondering whether they will keep this mural in the new neighborhood.