The song featured in the end credits is "Stay" performed by Ghost featuring Patrick Wilson. It is a cover song originally from the band Shakespear's Sister.
The college featured in the film is named after Jane Pierce who was one of the former First Ladies (1853 to 1857) during Franklin Pierce's term. She was an occultist who would hold seances in the White House to communicate with her dead son.
In each scene, rather than each frame, there is something red. The use of a red 'thing' is subtle and purposeful.
The movie marks the return of Lambert family since Insidious: Chapter 2 (2013), after that Insidious: Chapter 3 (2015) and Insidious: The Last Key (2018) are prequels set before Insidious (2010).