Prince of Persia: Warrior Within

- Missable -

The keyword here is "Hidden". Under the Extra menu on the main screen, there are various artwork sections. Your goal is to fill Environment and Characters sections as they are the only "hidden" ones. Artworks can be found inside chests, scattered around the whole game. Even if some are a bit out-of-the-way, their locations are obvious. See here for a text Guide (credit to LordMaceX): LINK

Also use these video walkthroughs made by FluffyKSA:

Please note that before the final part of the game (right after the mask part), you can still go around and gather some of the chests. Some others instead are missable, like the ones on the "crumbling" section of the game. Also note that Artworks carry over with every playthrough, so if you skip some simply check the position of the missing art in the artwork section and find its location on the guide I posted above.

Chests are also saved into a system file the moment they get opened. If you accidentally die or forget to save, they'll still count as saved and count towards the trophy. Credit goes to jigsaw for confirming this last part