It seems like this puzzle is too open-ended to be solved by a single player, so it might be a good idea to share tips and hints here in the comments.
For starters, I'm pretty sure the poster on the wall ('look poster') is going to be important...
[EDIT] Came back to it and was able to solve it on my own, although I used a lot of help from the Discord channel, especially to find how to get started!