I use SoloSlides for Google Photos. It's free to try, but I ended up purchasing it to get the randomisation feature. I've created a separate Google account where I add pictures that I want to show on the iPad.
It's fairly stable. Only really run into issues when the internet goes out and then comes back later, sometimes this would make the app stop showing photos.
I have an old iPad, haven’t been using it so this gave me an idea.