At the end of the movie, The Innkeepers, why did the door to the room where Claire was staying in, close? What did it symbolize?
While most reviews I've read deal with the artistry and the tension of the film, two reviews I found offer similar interpretations of the film's symbolism.
This reviewer contends that the door closing symbolizes Claire's being shut out of the upper class "to which the inn historically catered" - further symbolized by the Blue Boy painting in the room, which represents luxury. The closing of the inn itself is symbolic of the end of the American dream and the ability to change classes, something the immigrant Madeleine was also unable to do.
According to Slant Magazine's reviewer, Claire is at a crossroads, with her life not turning out as she imagined, and the hotel, stripped and empty, symbolizes "vanished possibilities and remnants of a happier past."
The film ends with a deep stare into one of its rooms, before the door slams shut one last time; deepening his brand of horror with a sense of studied contemplation, West depicts a world continuously impinged on by the past, a realm we can admire but never actually enter.
If we look at the chain of events there, it seemed to me the inn has become cursed after Madeline's death. I think the unsatisfied soul of Madeline was searching to hunt another victim for a long time, but it was imprisoned efficiently by the inn-authority (maybe followed by a ghost-satisfaction-procedure!). But the sudden appearance of Leanne made things unbalanced. The ghost arose again, possibly sensing someone with psychic power came! So the soul started her hunting again. She killed everybody and made it look like they committed suicide. And the dead people also become like Madeline, an unsatisfied soul trying to kill others and make it look like suicide (remember, before the injury in her head in the stairwell, she was startled by an apparition of the elderly man). So I think the last scene, where the room is closed we can also see her apparition, signifying she has also become like Madeline and the others (ghost actually!) and will remain imprisoned, killing others like them.