I would like to trust that if someone asks for face pic and that person is asked for one in return and says yes that they will follow through and send a pic after they receive yours.
Unfortunately I have not found that to be the case ever. As in this conversation.
So if you ask me for a pic without first providing one to me you will not receive mine. And you'll be referred to this post as the one of many examples. If you have no intentions of ever reciprocating then do not ask.
And for those who have had the same experience feel free to post a pic of the conversation like this