The first time, years ago, they "lost" a packet of information we had to reconstruct at great pains, and then had to get a second physical because they lost the report from the first one. We only found that out after getting our state's federal senator's office involved.
The second time, we ran into both rapidly-changing immigration requirements[0] and a pandemic, which made it super-unclear which issue was more relevant to the seemingly-interminable wait of years.
The instructions are vague in the best of times, and even immigration lawyers have no idea what a given USCIS staffer will care about on any given day. A rejection can mean anything from another year or two in the queue to a demand to leave the country and the life you've built within 30 days, so the stakes are high.
In my most recent application packet, I did include a photo I wouldn't publish online. While it featured no nudity, it was taken in bed. The same photo rotates through a digital frame on my desk in a house with a child in it, so it's by no means risque, but that is why people send in photos you might consider unwise.
0. I can't think about this without offering my best wishes and condolences to Mrs. Miller, who married the architect of that immigration nonsense the same year I married my partner.