1. A method for generating a mosaic image with an appearance that approximates a target image by utilizing a plurality of source images and a computer, comprising the steps of: loading the target image into the computer; dividing the target image into a plurality of tile regions, each tile region representing a distinct locus of the target image, and for each tile region: dividing the tile region into distinct sub-regions; comparing generally complex source images to the tile region to produce a measurement of visual similarity, said comparing step including comparing each sub-region of the tile region with a corresponding portion of each source image to produce the measurement of visual similarity; selecting the source image with the highest measurement of visual similarity to represent the tile region; and positioning the selected source image in the mosaic image at a locus corresponding to the locus of the tile region.