Here is a Multiscale Mosaic of Obama created from hundreds of pictures taken during his time in office.
The Van Gogh Portrait Mosaics were fun but I wanted to try an example that uses photographs as opposed to paintings. I settled on a portrait of Obama because of the widespread availability of photographs of him that are free of copyright restrictions. The subimages for this design are taken from the White House's Flickr photostream and seem to have been primarily taken by Pete Souza. I downloaded the 1000 most 'interesting' photos from the stream and used those as input to my process. I also manually selected and hand-centered about 10 interesting regions from these images to augment the set.
Here is a close-up showing the detail near the eye and nose.