It’s the Forest app! I used it long ago.

Just the “Nature” collection from iOS. I love oceans so it’s mainly oceans & seas from all places. (And occasionally snowy mountains)

Self-plug: PENEfiles! (yes it’s an unfortunate name but I didn’t know back then cuz I am not a native speaker). Comes with a tag system and file ownership management. Supports direct link sharing, and the whole website can be visited without logging in. Here is a detailed intro and here is the source code.