In Hurley's Polaroid, the background appears to be blacked out and paint peeling off the walls. But in the flashbacks, the facilities are clean kept. This would be due to the fact that we are seeing the facility as Hurley remembers the facility. The picture with the plate moved and the changed walls are due to what really happened. We will find out that the facility is not as nice of place as Hurley remembers.
I agree that the Polaroid seems staged. There are many subtle differences between the Polaroid and the actual sceen where the picture is taken. Could this be simply a prop error? Or another clue? However, TPTB did say that Dave is an imaginary friend of Hurley and not the Smoke Monster.
It could just be the quality of the photograph. Polaroids don't always turn out right.
The various manifestations that the "survivors" see (Jack's father, Kate's horse, etc.) are related to the shared hallucination
The buildings on the Island that resemble hospital facilities, like The Staff and The Arrow, are the stand-ins for their real-life counterparts in the hospital
The Others are actually the nurses, staff, etc. of Santa Rosa Mental Institute
In the second jigsaw puzzle, all images are of the Others, except for one of a sign from the Santa Rosa Mental Institute.
This is a type of group therapy. This explains why people "die" soon after having a breakthrough.
In an article in Entertainment Weekly magazine, a network representative denies that any character will wake up and find they're in another place. The producers have also stated that (most of) the events are not hallucinations. "The stakes are real."
Someone at the hospital may be a DHARMA recruiter.
Dr. Curtis bears more than a passing resemblance to Marvin Candle, especially if you consider the twenty or so years between the DHARMA orientation films being made and Hurley visiting the hospital.
These things, like the numbers in most instances, are just easter eggs (fun little in-jokes the creators use to keep their core audience smiling) and hold no real significance.
The Santa Rosa Mental Health Institute is located in Santa Rosa, CA not in the LA area. When Jack went to visit Hurley in Something Nice Back Home, he drove from LA to the Bay Area. When Sayid pulled Hurley out of the mental hospital, they flew back to LA which was where the safe house was located, and also where both of them live. The location of the mental hospital is not a continuity error.