We have a wall timer for our kids so they can see how much time left they have for activities. My wife was using it this morning and took it off to use it in another room, and she noticed condensation on the back. My first thought was that the wall had a leak, but on further inspection everything looks dry except the area behind all of the other pictures on the wall, which were all ruined by mold on the backs. A few minutes of research later tells me that cold air can get trapped behind pictures and art on the warm exterior wall and allow condensation to build up and mold to grow. New fear unlocked I guess.

Oh, no!
Good post & alert.
Back when rockwool was in vogue, no reports came about this, except in spots where the insulation was missing "somehow".
Good luck

https://engineerskill.blog/insulation-water-absorption-guide

Almost 30 year old tract home, so probably. It is also a wall that gets a **** ton of sun. There's basically 0 shade on that side of the house. After we replace the pictures I'll have to put some kind of spacer on the back of the frames.