Stitching images seamless animation

[doodle]

I am looking to make an animated caustic map. I know pretty much how to make it but need it placed perfectly. I need to put an image 256x256 image on lower left of my canvas, then place another 256x256 image on the right side of the first image and continue for 8 images, then add another line starting on the the left for a tota of 8 lines with each line having 8 256 x 256 images, so when finished will be one giant image. Is there a way to get the images to snap into the correct space? I am having a little trouble getting them exactly placed.

Thanks