Have a look at these great images (on Fubiz) in the series “Enlightened Souls” by French photographer Fabrice Wittner. He uses images of people with a stencil-like effect and puts them on a background of a real photo.
This effect might be very useful in presentation design. It is very hard to a series of images with a consistent look and feel on either stock photo sites, or Flickr. Moreover, I find that using images with real people not working very well in slides. It is too personal. This slight distortion of the characters might just solve these 2 problems in one go.