The Elysian Fields are the part of the Greek mythological Underworld where the souls of the heroic and the virtuous go.
While addressing the gods, Dean says: "Alright you primitive screwheads, listen up!" This is a direct quote from the Sam Raimi film Army of Darkness (1992), the third installment of the Evil Dead series.
When the boys discover the hostages in the kitchen freezer, Dean makes the comment "Motel Hell." This is in reference to the 80's campy slasher movie Motel Hell (1980) about cannibalistic motel owners.
Gabriel tells Dean he is "blowing Jonestown" a reference to the notorious mass suicide led by the leader of the cult, Jim Jones. There were 909 killed with all but two deaths caused by cyanide poisoning. On tapes recorded prior to the event Jones and other members referred to this suicide as "revolutionary suicide". In Hammer of the Gods the location is in Indiana, and Indianapolis Indiana is where The Peoples Temple cult was formed. In 1977 members of The Temple moved to Guyana where Jonestown was erected in an effort to escape the building pressure and allegations from various sources. Many of the members of The Peoples Temple believed that the promise from Jones that Guyana would be a utopia, or paradise. This corresponds with what is happening between the angels, devil, and the gods.
When Gabriel says, "I'm the Costner to your Houston," he is referring to the film The Bodyguard (1992) starring Kevin Costner and Whitney Houston.