you can try the Photoshop cs2. Look under filter mode of the program. There are many means of creating interesting texture, mozaic patterns, artistic stuff into your image. These in term can also be varied - eg mozaic tile size, grout size, etc etc tt enable you to make the patterns you desire. You can also combine various patterns together. Technically, the number of ways to combined the variations is extremely large. Happy experimenting.
Is there software that is able to do most of the processing for me?
As in, I choose the picture I want the final mosaic to resemble (eg in the pic above, the face of bill gates), and then i give the software a whole resource pool of photos, and it does the rest for me.
Work with photoshop cs2 is a bit tricky because I dont think it can help me with the compilation of like which image goes where in the mosaic right.