Mosaik photo is is a picture (usually a photograph) that has been divided into (usually equal sized) rectangular sections, each of which is replaced with another photograph of appropriate average color. When viewed at low magnifications, the individual pixels appear as the primary image, while close examination reveals that the image is in fact made up of many hundreds or thousands of smaller images. http://en.wikipedia.org/wiki/Mosaic_photo

You can make cool mosaik photo simply with the software calles Foto-Mosaik-Edda. This is a donationware program, so you can freely download and use it with an optional donation to the author.

Launch the program, make a database as library for images/photos which use as the tiles image (more photos in library, better the result will be).

Choose the photo to make as the canvas and set the amount of tiles, resolution, and other settings.

Then you have a cool mosaik photo.