"What are the advantages of photo attachments over photo links?"
I did this, with some pictures I put in another forum where I don't identify myself as Gustavo. For some reason (mainly, I think, because, when I was returning to Playmobil, I wished to be myself wholy, no disguise at all), I registered with my name, and, at the time, the most common password I happen to addopt. (I recently changed it, because of some confusions that took place: I put it as different as I could from the one of the service from which a hacker has been identified.)
But I make part of another forum, where I don't want people to think I'm myself. For no special reason, only, maybe, I'm more of my (child[ish]) self here than there. I'm not known by my name, there, and I use one pseudonym and one "eke" name ...
Once, I posted pictures here, attached, thinking about not having it public. By then, before entering the other forum, it was ... something that made me think that I didn't want anyone besides you playmofriends to know about the pictures. Recently, I saw myself in ... some sort of need to publish some playmobil pictures there. The only ones I could publish were these (from which I selected one), because they were the only ones that weren't public, as for example, all my pirates' stories are ... If I publish any of my pirates, everyone will easily know that it's me.
Not that it is impossible to find out that I'm that guy in the other forum, and/or vice-versa ... It's the same author, the same way of writing, some same "virtues & vices" ... But it'll demand a bit of an effort that most people won't spend in doing.
(If someone makes a thorough ... and not so thorough investigation, it's easy to see that I'm the guy in the other forum, with the different name, and/or that he is me ... But I don't want simply to say that. 'Don't know why, or have an immediate reason for this, besides ... some sort of care for my individuality, and particular (public) life ... (Because, whenever you're in a forum, your life, and opinions, become public.)
Gus