An Oakland Raiders cheerleader performs during the second half of an NFL football game against the Pittsburgh Steelers in Oakland, Calif., Sunday, October 27, 2013. (Photo by Marcio Jose Sanchez/AP Photo)

A grave cleaner holds up a skull during exhumation works at the Cemetery General in Guatemala City May 24, 2013. If a lease on a grave has expired or not been paid, grave cleaners will break open the crypts to remove and rebury the bodies. (Photo by Jorge Dan Lopez/Reuters)

A view of an installation as part of the “S.A.C.R.E.D” exhibition by Chinese artist Ai Weiwei during the 55th La Biennale of Venice, in the church of Sant'Antonin in Venice May 28, 2013. (Photo by Stefano Rellandini/Reuters)

A demonstrator is detained during May Day rallies in Santiago May 1, 2013. (Photo by Ivan Alvarado/Reuters)

The Eiffel Tower is illuminated during the traditional Bastille Day fireworks display in Paris, July 14, 2013. (Photo by Fred Dufour/AFP Photo)

Coffins are lined up near the wreckage of the bus, on July 29, 2013. (Photo by Salvatore Laporta/Associated Press)

A “Free Syrian Army” fighter in the Bustan Pasha neighborhood of Aleppo, Syria, August 21, 2013. (Photo by James Lawler Duggan)

A Chimpanzee opens its Christmas presents at ZSL Whipsnade Zoo on December 17, 2013 in Bedfordshire, England. (Photo by Tony Margiocchi/Barcroft Media)