"The Ghost of a Flea" by William Blake, as tattooed on the back of "The Bridge" character Eleanor Nacht (Franka Potente). Kindly identified by tumblr genius anon-hex.
Painting synopsis from the Tate Gallery: John Varley – an artist, astrologer and close friend of Blake – reported in his Treatise on Zodiacal Physiognomy (1882) that Blake once had a spiritual vision of a ghost of a flea and that ‘This spirit visited his imagination in such a figure as he never anticipated in an insect.’ While drawing the spirit it told the artist that all fleas were inhabited by the souls of men who were ‘by nature bloodthirsty to excess’. In the painting it holds a cup for blood-drinking and stares eagerly towards it. Blake’s amalgamation of man and beast suggests a human character marred by animalistic traits.