iPhone/iPad lock screen as a digital message board I use my iPhone/iPad screens as digital message board. A bit like digital message boards you might see in airports, doctors waiting rooms or train stations.

My current strategy is to open a photo editing app on my iPhone, write a message, save a jpeg in the photos app, sync the photo across my iPhone/iPad and then assign the photo as wallpaper for the lock screen.

But I'm wondering if there is an app which I can display messages as wallpaper in the lock screen and sync across iOS devices?
Currently, apps cannot change the wallpaper as you describe. I do not believe it's possible for wallpaper to be synced between devices, either. (You can sync the photos being used, but I don't believe you can sync the choice of wallpaper.)