If you see a painting, examine it. Actually, I wouldn't have been able to end the game if I didn't examine this painting. All the problems and quests have to be logical. Even if the problem sounds difficult it can be very easy. But watch out for misleading theories.
Mazes are a feature for itself, found in almost all textual adventure games.
I think the mazes began to be used much since the game of Zork, but I could be wrong. We all know what are mazes in real life, but mazes in textual adventures are rooms with the same or similar descriptions, bound together, forming a maze. In some mazes you will reach the walls, but some will keep repeating the boring same description, like You are in the maze of narrow passages, all alike. As you move, you keep getting the same description on the screen. Eventually you get lost and don't know wether you are moving or not.