Visible crew/equipment: In several shots during the weight room scene, a boom mic is reflected in the hanging swords.
Revealing mistake: The roller coaster used for the Devil's Flight is really the Corkscrew at Playland in Vancouver, where all three movies were filmed. If you look during the opening credits, you can see the name "Corkscrew" up in the lights above the coaster. After this, it says Devil's Flight during the rest of the roller coaster scenes.
Visible crew/equipment: When both Kevin And Wendy are looking at the pictures after the funeral, Kevin asks Wendy to look at Frankies picture. Kevin then turns the car a little to the left almost hitting the tow truck, seen in the metal bumper you can see the front of the camera truck.
Chosen answer: It's metioned in the filmakers' commentary that in every Final Destination movie everyone has a premonition (Of course), well it's also mentioned by the director, James Wong, that if death wants to kill them why give them the premonition in the first place? Well he believes that there is some other force out there trying to prevent death from killing these teenagers. That's where the premonitions come in including the signs therefore, Wendy's pictures are helping signs like voices or visions from other movies. It's just the whole "giving signs" thing is portrayed differently in this movie.