In order to create the feeling of the holiday season, Christmas decorations were kept in some streets of Bruges until the end of March. The town council made an official communication to the people of Bruges explaining the reason why.
The painting that occasions comment even from Ray is "The Last Judgment" by Hieronymous Bosch. Bosch-like symbolism recurs throughout the movie (the dwarf is one example), suggesting that Ray and Ken may indeed encounter their own Last Judgment - or that the waiting period in Bruges is akin to purgatory.
Except for the flashback, Ray wears a single outfit throughout the whole movie. While he does remove his jacket and unbutton his shirt, he has no other change of clothes. Ken, on the other hand, has several wardrobe changes.
When the characters visit Groeningemuseum they are shown viewing paintings "Death and the Miser" by Jan Provoost (ca. 1515), "The Flaying of Sisamnes" by Gerard David (1498), "The martyrdom of St George" by Unknown artist (1500-1510), and "The Last Judgment" by Hieronymus Bosch (1482).
Harry's strict moral code gets a further insight in a deleted scene, where a young version is played by actor Matt Smith, best known for his role as the 11th doctor in 'Doctor Who'. In it, Harry discovers his partner holding a dead woman in a club, so he marches into a police station and beheads the man who did it, a dirty detective. Ultimately, film makers decided to cut the scene, as the CGI decapitation looked fake.
Ken and Ray check into the hotel under the names "Cranham & Blakely", presumably after actors Kenneth Cranham and Colin Blakely who played two hit-men in a television adaptation of Harold Pinter's The Dumb Waiter, one of the film's major influences.
A scene was filmed with Harry on a train on his way to Bruges, where he is verbally aggressive to a fellow traveler who attempts some small talk. This scene was cut from the theatrical version of the film.
When talking to Harry (Ralph Fiennes) over the phone, Ken (Brendan Gleeson) mentions that Ray (Colin Farrell) was initially put off by a recently built dual-carriageway. A scene in the beginning would have showed Ray refusing to get into a carriage to get from the station to the central town, but it was deleted from the final print.
The Tottenham joke is referring to Tottenham Hotspur Football Club, it is a football team in the English Premier League that was -during the movie era- a team that's always good enough to reach near the top 3 teams but never actually really reaches there, it was a good team against all the other teams that are under him but never good with the top teams.
The trivia items below may give away important plot points.
When Ken receives the phone call from Harry, the opening scene from Orson Welles' Touch of Evil (1958) is playing on the TV, possibly one of the most famous scenes made with one continuous shot. From this point on, Ken's phone call with Harry is one continuous shot, in a homage to 'Touch of Evil'.
The last scene where Ray stumbles on to the set and he sees all the costumes: the imagery is akin to the paintings of the last judgement; the animal heads, animal skulls, peasant looking people. Plus the dwarf dressed as a schoolboy represents his sin right before he is shot (his judgement). However, he attempts to save Harry by telling him that the dwarf is not a child despite the fact that Harry tried to kill him, thus redeeming himself, so he lives. Plus he notes that waiting in Bruges may be hell for him, however it was more than likely Ken's idea of Heaven. The waiting in Bruges before his judgement may represent purgatory.
In a deleted scene, Ray and Ken are lying in their beds discussing Ray's murder of the priest and the little boy. Ray ponders over why he was sent to kill the priest, guessing it was likely pedophilia. Ken counters that Harry was behind a land-buying deal that the priest opposed. These two explanations are coincidentally two different motives that are suggested for the archbishop's murder in Primal Fear (1996).
Blank bullets can actually be quite deadly. In 1984, while on the set of the short-lived series "Cover-Up", actor John Erik-Hexum unintentionally killed himself when he playfully fired a gun loaded with blanks into the side of his head. The force of the blast blew a plug of bone into his brain, killing him.
When Ray first meets Chloe, she explains that the film being made on the streets of Bruges is a sort of homage to Don't Look Now. In both that film and this one, the main character grieves over a child's death early in the film, stays in a city with medieval architecture, and dies at the end in a scene involving a dwarf who is confused for a child.
During Ken's suicide scene, the coins that he drops (to clear the way) before jumping are the same coins he tried to use earlier in the film when trying to gain access to the same tower, but since the amount was insufficient, he had to pay in notes. Therefore, if he had been let into the tower earlier using coins instead of notes, he wouldn't have been able to jump at all.
Once Harry arrives in Bruges and confronts Ken, they move towards the clock tower before the attendant informs them the tower is closed that evening due to an American suffering a heart attack the day before. This is likely a reference to the overweight American tourists Ray insults and is then chased by.