Continuity mistake: When Sy is following Nina and Jake after he put the picture of the husband cheating in with Jake's pictures, the cars pull over to the side of the road. If you watch when they pull over, you see that they pull over next to a down sloping hill that is nicely green with grass and a few sporadic trees. But when they show Sy's car in the rearview mirror, you see that they are now pulled next to a large up sloping hill that is covered in leaves, dirt, and a lot of trees. (00:53:40)
Continuity mistake: In the scene where Sy is giving the toy to Jake after the soccer game near his car, he hands the toy to Jake and Jake says he can't accept it etc. Then we see Sy put the toy back in the Savmart bag, but when the shot changes the toy is still in his hands, not in the bag. (00:35:05)
Continuity mistake: Near the middle when Sy is imagining he is in the Yorkin's home, he is sitting on the couch watching a ballgame. Behind the couch is a tall white square sculpture. Sy turns to the dog and says, "Good game." When the camera goes back to Sy, look behind the couch, the sculpture has disappeared. But when you see the Yorkins come in the door, and the camera goes back to Sy on the couch, the sculpture has reappeared. (00:30:15)
Continuity mistake: As Sy is developing Nina Yokin's birthday party negative the film canister shown has the green and white Fuji colors and layout. When Sy holds the processed negatives up to the light to view the exposures the film information along the side of the strip indicates the film is Kodak Portra 400VC. (00:06:50)
Continuity mistake: As Sy is watching tv (just before he turns onto The Simpsons) there is a glass of coke on the sidetable sitting on a napkin. The next shot its moved a bit to the left almost next to the napkin. (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.