I've found two more glyphs (nails, dagger). Still don't know what to do with this. 

 

I found it!

The vault is open... hehehe 

I found all the symbols, the switch and the secret, but I still haven't found the secret level or what the symbols are for. I have a feeling it's something to do with the gate in the room you arrive in when you come in, but I'm not sure if I'm on the right track. A little hint would be appriciated 

The code is found with the help of the main hud in the game.

And it will just unlock the vault file in your installation (arts and design of the mod).

It's unrelated to the secret level in the tart map. The secret level is found in the basement, in the TV room. 

Wow I've been to the TV room so many times and somehow this was the first time I actually went on that spot.

I'm still lost with the codes. I've found claw, soul, nails, azathoth eye and dagger. I think I'm missing two maybe, because there is one on the main menu screen that I've not found yet and there was nothing there for eye. My question is still how do you write this? Where? 

When you try to extract the Artwork zip file you'll need a password. The password is made up of the clues found in the symbols.

I don't want to say more in case I offend the creators. :) 

Got there eventually, figured out what I've missed.

I'm still sure, though, that there is a way to unlock the gate in the difficulty select room. Or at least the door. Unsure what else is there that I could pull at. 

That code reminds me of the old Myst game. 

Kinda frustrated by the ambiguity in this thread and how the mod authors gave their hints. This post is for those like me.

There are 7 glyphs you can find around the Monument start map. The background of the main menu, along with the highlighted letter associated with each glyph should give you the password to access the "Art Vault" archive in the mod folder. All capitals, input order starts with the bottom left and goes clockwise.

My frustration comes from the main menu background not showing all 7 glyphs. Even changing the display aspect ratio doesn't show the top glyph. Pair that with my dumbass thinking there was an eight glyph i was missing because of the octagon background. Grrr!

If you're having trouble finding the glyphs, their locations are as follows:

1: right after starting a new game, before jumping down the pit there is another ladder leading to a balcony with a glyph.
2: after jumping into the pit, hug the wall on your left and you'll find another glyph above the dresser.
3: walk through skill selection straight into the main hall. There are two raised planter boxes with "Main Gallery" signs on them. Inside the left planter is another glyph.
4: Inside the TV room before the credits graffiti, the inside wall next to the door has another glyph.
5: fall into the floor in front of the TV. Defeat the enemies then go to the library on the right. Jump up the furniture at the back left of the room. The glyph is on the floor of the upper level.
6: Make your way back towards the main hall. At the bridge just past the instruments, jump on to the ramping wall detail on the right. Hug the wall until you enter the hall above the other end of the bridge. Keep an eye on the wall opposite you and you should see the next glyph.
7: easy to find on the balcony above the QBJ Resurfaced section.

Short of outright saying the password, I hope this helps some folks get into the art vault. Plenty of cool concept art and other goodies worth seeing if you like art.