Fruit stack method worked amazing for me! Sometimes I would open my mailbox and even get two photos in one day. Not to mention, it's also kind of fun to wait in anticipation for the next day to see what I got!
My sure fire way to get a villager photo is by wrapping a stack of 2 non-native fruit. I believe the earliest I got a photo was 2 weeks from this method, while the longest was over a month. I'm pretty patient with it though it's a guaranteed method, it's just a matter of waiting for the right moment.
Talk to them everyday and give them wrapped presents. Also, play with them when they want to. Marshal gave me his photo through a game of hide and seek it was super cute it was the “treasure” he made me find.
you’re not doing anything wrong; like others have mentioned, it honestly all boils down to rng and while it’s definitely frustrating, hopefully you’ll be able to get antonio’s and sydney’s photos soon! as for me, when trying to get a villager’s photo, i’ve stuck with giving them a piece of foreign fruit each day, talking to them 5-6 times (in hopes that they’ll ask for a favour) and it usually takes around 3 weeks to a little over a month for it to work aha. but honestly, you’re not doing anything wrong and i hope that you’ll have better luck soon! :>
For me, I've just been gifting any villagers I don't have a photo for a wrapped stack of 2 non-native fruit daily. It usually takes me a month from when they first get onto the island to get their photo, though sometimes it can take longer. But that's fine, I'm more than willing to be patient with it since it's worked for every single villager I have or had (16 so far, working on my 17th).
I used coconuts. I'd fill my pockets and give one to each villager. As I got photos (and it took a while), I'd drop them from the daily coconut gift. I didn't want to mess up houses, so that was the safest route, for me.
I started the fruit stack trick a few days ago, and I got Audie's photo before she even asked to change her catchphrase! If anything, it's definitely helped raised their friendship levels faster, and seems to work as well as people claim it to.