This is a quick way to cut up a photo mosaic into an image sequence:

1. Place the large image a comp that is the size of the tiles you want to cutup.
2. The comp should be this many frames in length: (thisLayer.width/thisComp.width)*(thisLayer.height/thisComp.height).
2. Add the expression below to the image's anchorPoint.
3. Render out an image sequence.