Factual error: The Point & Shoot Camera Sy uses throughout the movie (Minolta Freedom Zoom 150) has a lit in-viewfinder readout. The real camera does not have any fancy readout, just a thin circle to help center and frame your image.
Factual error: When Sy is watching the Simpsons in his apartment, the clips we see, while all from the same episode, are spaced further apart than what we see. [Some people say they're from different episodes - a mistake regardless.] (00:17:05)
Chosen answer: This is mentioned on the DVD commentary - it's deilberately open ended so one can interpret it as either it's Sy imagining what he wants to happen OR it's what really happened.
Neil Jones
As Neil Jones said, the ending is open for interpretation. However, I think there is reason to believe that Sy imagined the photo. It shows him and the family outside of their house, all looking happy together. Would they want to take such a photo with Sy after the incident at the hotel? And before the incident, they were probably not close enough with Sy that he would be in a photo taken at their home. Him and no other guests/visitors.