"If a picture is worth a thousand words, an image mosaic is worth a billion words!"
If you obseve this Firefox Logo image carefully, you will notice that it's composed of hundreds or thousands of individual images arranged as tiles so that they appear as one picture when observed from a distance. This beautiful blend of images together is commonly known as a photomosaic or a photographic mosaic.
The individual images are totally unrelated to each other, but when stitched together, they perfectly resemble the final image.
Though the final image looks complicated, it can be created in seconds using the free Image Photo Mosaic Generator - an highly addictive online tool that converts any photograph into great looking photo mosaics. Just upload any of your JPEG images and this mosaic tool uses photographs from Flickr to construct the individual tiles of the image mosaic.
Photomosaics can also be a unique gift. But stay 15 meters away from your computer and look at the image mosaic for maximum effect.
Related: Recursive Photomosaic - never ending chain of interactive photographs.