A simple python script to create a mosaic.

Here's a sample command:

python mosaic.py -i input_image.jpg -s my_directory_of_images_to_make_mosaic_out_of -r 10 10 -t 20 20 -v -a

This will make a mosaic out of input_image.jpg using the images in my_directory_of_images_to_make_mosaic_out_of.
It will analyze 10x10 boxes in input_image.jpg for the closest match in the directory of images. In the mosaic,
it will save 20x20 image thumbnails. Thus, the output image will be bigger than the input image (by 2x in each dimension).