IMosaic

IMosaic is a great free program that allows you to create an incredible mosaic master piece from different image tiles.
The process is simple, first you have to select the image source which will be the example to create the mosaic.

Then, you need to select the block width and block height for the mosaic and set other parameters such as output scale, image quality, etc. Next, you need to add an image collection file. The images contained in this collection file will be placed in the right position according to their color to produce the mosaic effect. After you have added the collection file you just have to select the "Process” option, and finally the Mosaic will be created.

If you don't have an image collection file already created, you can create a new one by using the Image Collection Editor which can be accessed from the Edit menu. Here you just need to add the images or select a directory with images, process the images, and finally save the collection file.

You can use different collection files to produce the mosaic. All the images are merged to a database. The program can use an image more than one time to make the mosaic more similar to the example image.

IMosaic supports bmp, jpg, gif, jpg, gif, tif, and png image files.