For example, when we see Chris in a similar position as her sister before her suicide. Her position mirrors the dead sister, perhaps giving the audience a sort of foreboding aspect to this character.
Another interesting thing was the use of color. To me, it was most notable with Chris, who would dress in different yellow outfits that would match her surroundings. It seemed carefully composed to give the eye the illusion of a painterly image.
The end of the film reveals that Walker never does leave the island, but he just dies, and all that we watched was his last thoughts, of what might've been his final mission of revenge.
This 'dream-like' aspect of the movie can be seen through it's structure. As stated before, the film becomes more and more fragmented, as does the narrative. Scenes from earlier in the movie flash up again. For example, when he is about to kill someone, the fight with the two thugs in the nightclub plays again.