The repeated scene of Doomsday pounding against his cell, complete with a "DOOM" sound-effect, is a reference to Walt Simonson's run on The Mighty Thor. Simonson's wife, Louise, was one of the writers of The Death of Superman.
In a few panels, Jimmy Olsen is shown wearing a Spin Doctors shirt. The band had a hit song at the time called "Jimmy Olsen's Blues". (One might wonder why Jimmy didn't wear a Crash Test Dummies shirt, since they did "Superman's Song" the year before, which was about Superman's funeral.
The Cyborg Superman basically looks like the Terminator in a Superman costume.
