Some spoilers for Anna to the Rescue

Picture 1: Bring up the compass that is in your inventory, and press the pillar buttons in the following compass ways: N/S/W/E
Picture 2 & 2a: there's a small switch near the skulls wall, that opens a decorative panel (see the picture 2a)
Picture 3 & 3a: there's a small switch near faces column, that moves aside a nearby wall and painting (see picture 3a)
Picture 4 & 4a: there's a small switch near a skullystatue, that opens a decorative panel (see picture 4a)
Picture 5, 5a & 5b: use the switch near the red Face, to open some nearby grates ( see picture 5a) , and use again the switch to open the other grates that will give you acess to one of the treasure locks (see picture 5b)
Picture 6: get the treasure lock key behind the wall.
Picture 7: shoot the four buttons and a window behind you will open .
Picture 8 & 8a: Put out the fire with a waterarrow, to make the hot switch frobable (se picture 8a)
Picture 9: rope up to the wooden beam, and open the wooden panel that has the quake 1 symbol, to reveal an exit, where you will find inside a switch that opens another grate.
Picture 10 & 10a: there's a small switch near the monkey face skeleton, that moves aside a nearby painting (see picture 10a)
Picture 11: the yellow line shows you the right path to follow.
Picture 12: there's a small switch behind the grate that opens a door below.
Picture 13: the yellow circle shows the right key to obtain.
Picture 14: The jumping key can only be obtained from behind the metal bars.
Picture 15: This torch switch moves up the wall in the corner.
Picture 16: there's a small switch near a torch that opens a decorative panel

The Gallery painting puzzle:

Pictures a, b, c, d, e and f are named in alphabet order to show the right way to frob them.

Artifacts ot obtain in "hard" and "expert" mode:

Picture 17: rope up the wooden beams in order to acess a secret area where you will find the unholy glove, aquiring this item will allow you to obtain the sleeper. Picture 18: rope up, to open the golden grate, that will reveal you an air passage, inside you'll find the lost keeper.