The Pyramid Head monster actually has an eye and a tongue. The eye is barely visible on the front of its head and the tongue sticks out and wiggles when it grabs the player by the neck.
Many of the corpses the player can discover throughout the game are the same character model as the protagonist James. All of them though are so dismembered/bloody/dirty that they're hardly identifiable or oblique camera angles are used to prevent the player from getting a full view.
The Blue Creek apartment building in Silent Hill is a reference to the film Blue Velvet (1986). "Blue", for the movie's title; and "Creek" as a synonym for "River", for the Deep River apartments seen in the film. The apartments in the game are very similar to the look and overall layout of the Deep River apartments in the David Lynch film.
The straight-jacket monster was inspired by the art director seeing an employee at work coming towards him in a hoodie while bobbing around listening to his personal stereo.
When James is holding the chainsaw and is standing over a body for a few seconds, he holds it over his head and screams out. This is a reference to Leatherface in the Texas Chainsaw Massacre series.