I just thought I'd share this idea for photos that I've been using with people I've traded communications with over the past year or so.
If you want to be sure that a picture of someone is legit, just ask for one with something specific and common, but unusual for someone take a picture with. Have them hold a bar of deodorant, balance a fork on their finger, or write "hello" in the dust on the back of their car and pose next to it. This makes it very unlikely that they'll have an old picture meeting the criteria or be able to find a stock photo that meets it. This can't stop people from doing a switcharoo like in the movie "The Truth About Cats & Dogs" but at least it guarantees a fresh photo. And finding a fake with an accomplice photo model is very unlikely.
When I offer a picture of myself, I ask if they'd like me to take one like this with an item of their choice so they know it's a fresh picture and most likely actually a picture of me.