An interesting take on double exposure by graphic designer and illustrator Alon Avissar, worth a look!
Recently I have been playing around with different techniques for exposing multiple images in a single piece. I found that blending someone’s image along with a background and negative space, made for some really interesting combinations. To make the images a bit more personal, I also used pictures of friends and family.
http://www.diyphotography.net/seasonal-beauties-wonderful-double-exposure-changing-seasons/