By DB do you mean a database? Because of course you can save photos to a database -- you have to, if you don't want to store them only locally. Facebook, Instagram, etc., do this all the time. It's hard for me to understand what you could have read that said that was bad. It's not a good idea to save photos to the Firebase realtime database, but there's a service Firebase Storage specifically for that, and you can save Blobs there. I use that for a project, and I save Blobs there, not base64 strings.
I think you'd really benefit from reading a book and/or taking a course. I'm most familiar with Josh Morony's book, which I liked, but there are other books too, and Ionic recently partnered with someone to produce a video course, see the Ionic blog. (And I think there's a video course at EggheadIO also.) Give yourself a coherent foundation.