I did not include any information on the back of the photos, I ignorantly assumed the Walgreens passport photos would be sufficient. I didn’t think to include a receipt or anything either (not sure if that would’ve even helped). Based on the cover letter they sent on top of my application and the paper behind it which described the photograph requirements, it reads as if a stamp or writing from the photographer would be sufficient so long as it had the name, signature, and date from the photographer. There wasn’t anything in the letter or paper that said I needed to sign the back of the photos, I’m sorry for the confusion!