I have asked for (and received) permission to share particularly yummy photos with specific people. It was fun.
"Hey, Cutie. I'm with my friend D. I was telling her how strong you are and she asked if I had a picture. May I show her the one of you goofing off naked, kissing your muscles?"
"Hey, Babe. I was telling Dani Debo and Cristina about last night. I showed them the picture of you at your brother's wedding. That's the one that comes up when you call or text me. They think you're hot! They want to see more pictures, but all I have on my phone are the [naughty] ones you sent all day yesterday. Can I show them? Would that be okay?"
I do show my friends normal pictures without asking for permission. I assume it is okay to show snapshots from outings and such. But I know the difference between a snapshot no one cares who sees, and one expected to be kept private. I always ask before sharing private photos, even if the subject cannot be identified therein.