I have just been own this road with my daughter. We were getting redd boys and they were asking for a photo, we asked our Rav who told us under no circumstances are we to give a photo. If they will not go out without seeing one and just by the shadchans description then it is not for us. If the shadchan never met the girl and wants to see a photo that is fine but it must be returned.I blamed it on my rav, if the boys mother wants to argue with a rav then over a picture I am not interested in that family.
B”H my daughter marrried the first boy she went out with and she was 19 without the boy seeing a picture.
What I know boys mothers do is find out when the girl who was redd to their son is going to a simcha and they will try to get a look at her while she is at the simcha.