Had to write my own bitmap processing library, since couldn't find anything fast enough off the shelf :-D Handled alpha blending, file i/o, etc (checkout the bitmap.lisp and color.lisp files in the repo).
Here's a video of it 'evolving' a picture of John McCarthy (best individual from each generation): http://www.youtube.com/watch?v=-_VFZ_ON0A8
And here it is doing the Mona Lisa: http://www.youtube.com/watch?v=S1ZPSbImvFE