find the largest picture & measure it- then take each picture individually & add borders/ blocks/ piecing around it to make it the size as the largest one- do this for each picture- then you can play around with the layout with a group of blocks that are all the same size you can make some into star blocks- square in a squares, log-cabins--what ever to make them each the correct size- if you want to surround the largest block too- do that first-then use that finished measurement.