Okay, about the unlocks, it seems it's really a bug or something like that. If the last Julian artwork is the bioluminescense sea, then it should've been unlocked in the gallery, but it didn't
Here's a screenshot of the scene that I just took after loading up a save I had: 
And here's a screenshot of the gallery that I took right after the scene: 
About the Nomax route artwork, I do have that one, actually! It was a tricky one, but it was a lot of fun. What I was referring to was the last one in the gallery that seems to be missing and I couldn't find it at all:
Idk if this bug is something that just happened to me for whatever reason but that's how things are for me as of right now lol. But if I didn't actually missed a scene then that's fine, it means I actually played (almost) everything that I had to play. Now I want more!
Anyway, that's the feedback I had to share. Thanks for responding!