If you plan to do this activity with high schoolers, who sometimes have difficulty remembering to bring things in, I would start asking for baby pictures at the beginning of the year. I had an assistant make copies during class time and immediately return their originals. Also, there may be students who do not have any baby pictures. One option is to try and get permission to make copies of pictures from their cumulative record- they often have elementary school pictures available. One student requested that she be able to find a picture of a baby online and use that as her picture, which we let her do.
I will continue to do this every year. It was nice to see students (especially ones with challenging behavior) in this light.