Any means of progressing normally go here.
The furthest I ever got through normal means was the second room. Noclip is countered by teleport barriers surrounding the map.
The painting hides a secret tunnel which leads to a black room with some decorative props. Past at first, it seems like nothing else lies in the map.
If you head opposite of the tunnel, another painting, the same as earlier, pokes out of a space.
Entering the space, seals you into another room with the painting. This time, you cannot move.
This is as far as I've gotten.