Double is interpreted in two ways in this post: as two objects that look very much alike, and as objects that appear doubled.
This picture shows two ships from the Celebrity cruise line. The ship on the right is the Celebrity Eclipse (Solstice Class), while the ship on the left is one of the ships in the Millennium Class. This photo was taken in an Eastern Caribbean port in November, 2011.
This photo shows two slot machines in the casino on the Carnival Pride cruise ship. The photo was taken in December, 2012, while the ship was in port in the Bahamas. (Cameras are not permitted in the casino when it is open for business.)
This photo shows a pair of boulders in a park just outside Las Vegas, Nevada. The car between the boulders indicates scale.
This photo shows a double chair in a park near the ocean in South Beach, Miami, Florida. The photo was taken in February, 2013.
This picture shows double blooms on a cactus. This photo was taken in a park outside Las Vegas, Nevada.
Finally, this photo shows two faces of Buddha, as well as two partial faces of Buddha. (Two more faces and partial faces are on the back side.) This photo was taken in Angkor Wat, Cambodia in March, 2013.