The name of the library the group is trapped in is "Savini Library" which is a nod to Tom Savini who has worked with George Romero on his zombie movies.
A nod to Rocky Horror Picture Show - actually several, with "Brad and Janet" being the popular couple, and Eddie uttering the phrase "Dammit, Janet!"
As the end credits begin you hear a women say "attention all shoppers," its sounds like the exact same voice that announced a free bag of hard candy in the original Dawn of the Dead.
There is a Return of The Living Dead ad on the back of the magazine Jimmy is reading in the library.
Ash is likely named after Bruce Campbell's character from the Evil Dead series.