Hi, Shockwave. Welcome to the forum. It's good to see you and I hope you enjoy your visit(s).
I like a photography app called FX Photo Studio ($2.99, USD). Yeah, it's to tweak and manipulate photo images, but it's got, to me, a great frame selection. You get seven included in the initial app, then there's two in-app purchases (each for $.99, USD) for frames (Classic and Art Frames), which brings you 30 more frames. There's wood frames, metal ones, plain, carved... You can save a picture to your Photos and then do whatever you wish with them.
I'm sure there are many, many others, but this is the only app I have and am familiar with. It's one of my go-to apps when I want to play around with photos. Good luck with your search.
Marilyn