Sequels?

[Azrael]

Flatliners was more of a dark sci-fi. Also, I wouldn't call The Lost Boys "dark gothic". He pioneered what one can call the "rock'n roll vampire" thing with that film (even a band inspired one of their tracks, and its music video, from The Lost Boys). The Lost Boys, Blade 1-3, Underworld 1-3, Dracula 2000, Queen of the Damned, I wouldn't call any of these "dark gothic". I see what you mean, though.

[BatmAngelus]

http://www.mtv.com/news/articles/1679248/nicolas-cage-scarecrow-batman.jhtml
Cage confirms that he was approached by Schumacher to play Scarecrow.

[The Joker]

This must have been literally right before he was signed to play Superman for Burton's Superman Lives. Which, if I remember correctly, was originally set for a July 1998 release.

[KeatonisBatman]

Does anyone recall that Keaton was supposed to be in the Burton Superman film?  I remember seeing an interview on MTV (I think it was with Carson Daly) and they were playing mini-golf together on the set.  Daly asked Keaton "Are you going to be playing Batman in the Superman?"  to which Keaton responded by repeating the question and said "Well, not exactly."  I can only think his coy reply meant that he'd be playing Bruce Wayne. 

[riddler]

I remember hearing about a batman/superman crossover also being considered at the time so it's possible especially with Burton at the helm it could have been Keaton reprising Batman.

[Azrael]

^ There was talk of a Batman cameo at Superman's "funeral", with Keaton in the role. Maybe just a rumor. I think a crossover was supposed to be done by Wolfgang Petersen in 2002-2003 for a 2004 (?) release. Eventually, and thankfully, it gave way to Batman Begins.