Hmm. I use Instant Book, so for the vast majority of guests I only ever see guests with a photo.
I will have to watch out next time I get an inquiry and see what happens.
I've never had to turn down a guest because I am uncomfortable with their photo to date.
I have turned them down because they wanted to bring three hampsters. Have the family she was visiting come around to cook and eat breakfast at mine with her every day, bring six month twins (I have no babies ticked), have their 21st gathering in my garden (hell no), because she wanted me to take her to her college course and pick her up every day (even though there was a direct bus there).
The point I am making is it usually what guests say or ask for that creates a red flag rather than what they look like in their photo.
If I was ever uncomfortable with a guest purely because of their photo, I would be happy to ask Airbnb to cancel.