I am going to jump into strangers' photos.
Why insert yourself into their photos?
I think I would look good in them.
Those are their personal photos. Those photos do not involve you. They are strangers and you should respect their privacy.
Is this not a funny thing to do though?
It may be funny to you, but that does not mean it is funny to everyone. Just leave yourself out of their pictures, you can take your own pictures of yourself.