Lack of Clocks & Natural Light: This is obviously so people lose track of time and keep playing.
This may have once been a small reason for this design, but nowadays it isn't fooling anyone. Most people have either a watch or cellular phone.
Oxygenated Air Supply: The idea being that oxygen will keep players awake and they therefore will keep playing.
This is not true. It is against the law to tamper with the air supply, however properties do sometimes scent the air.
Maze Like Design: Casinos are deliberately built to be confusing, so that players are more likely to keep playing.
Often the cages and bathrooms are on the opposite end from the exits
Curvature of Pathways: Many of the walkways are positioned on a gentle arc, this way when a player enters thee floor they are unable to see the entire floor, so you are therefore encouraged to explore.
Slot Banks: Slot machines are generally clumped closely together. This is twofold; to ensure maximum number of machines are used per square foot and studies have shown that players prefer intimate spaces to play in.
Lighting: Is set at a level where it is not too bright and thus would create a stark environment. Yellow bulbs are generally used to give a soft, even warm light. Many casinos utilise a moth lighting design, whereby the lighting is brighter towards the middle of the gaming floor. Here the principle is that people will more toward the light.
Sound: Slot machine bells and music are generally tuned to a certain key and rhythm, so that it isn't just a mass of noise but all plays together creating a unified sound that is pleasing to listen to.
If you wish to learn more elements of casino design, check out the book
"Designing Casinos to Dominate the Competition."