You may be referring to a stark image by artist Helmut Herzfeld (who changed his name to John Heartfield) who helped invent photomontage. He used the technique to make bookcovers for a Berlin publishing house which specialised in left-wing literature, and he also worked for several radical newspapers. As Germany plunged into Nazism, Heartfield's art became increasingly political, denouncing Hitler and the Party. He fled to Prague in 1933 and later to London. He died in Berlin on April 26 1968.
This may be the image you are referring to:
http://www.towson.edu/heartfield/art/arena.html