Skulls and skeletons are always my favorite subject of street art. Here are four examples, all photographed very recently, in various places :

(from left to right) :

(1) "The Skeleton Icon" : mix of collage and spray paint, photographed on Sept. 14 2014 in Paris, France. On the bottom of the frame it is written "L'amour court les rues" (litterally, "love runs in the street", meaning, "love is everywhere"). I don't know if it is part of the actual "Icon" art or something added later by someone else. Probably the latter.

(2) Tiny animal skull, paint sprayed through a stencil, photographed on Sept. 2nd 2014 in Evora, Portugal.

(3) Small Alien, paint sprayed through a stencil, photographed on Sept. 12 2014 in Lisbon, Portugal. Still counts as a skull, right ?

(4) "Waiting Skeleton", pink paint sprayed through a stencil, photographed on Sept 14 2014 in Paris, France. It is written "Attendre... la réussite. Il y en a qui sont morts comme ça" (Waiting for... success. Some people are dead from it) and signed "Meemy".