Have a swap pictures feature where a user can choose to send a picture in the chat but the receiving user cannot view the photo until they also send a photo. This will prevent users from agreeing to swap photos but not actually sending their photo after receiving a photo.
Chad chadd commented
Perfect solution. Should be free.
Agree with the previous comment, it's not doable.
Just gotta accept that there's a lot of people in this world who lack integrity!
Gio Gro commented
It could be useless: I could upload a bad mountains panorama and swap that and then block you. Sorry man, that's not the solution, unluckily