Warren White was a corrupt businessman who tries to avoid conviction for embezzlement by getting his case transferred to Gotham City. He thinks he's pulling a fast one by faking an insanity plea, but when he ends up in Arkham Asylum, he realizes he's made a huge mistake.
Passed around from villain to villain, he's tortured by Killer Croc who cuts gills into White's throat, basically Two-Face's bitch (or "coin boy") for a while, and he's locked in a refrigerated cell designed for Mr. Freeze. The frostbite gives White what would become his trademark appearance: white skin stretched to expose his teeth, a stump of a nose, and hairless head. Although he was only pretending to be crazy to go into Arkham, his time there ended up driving him mad.
Though he remains incarcerated, the Great White Shark uses his connections in both the professional and criminal worlds as well as his business acumen to run a criminal enterprice from his cell. His business's hitman, The Tally Man, notably killed a number of Batman's villains at White's order.
Pros: He's a striking looking villain.
Cons: His origin relies on being put into Arkham with a bunch of familliar crazy bad guys. Since, as far as we know, the Joker is the only villain to survive in these Batman movies and Heath Ledger's death would make Joker's return the longest of long shots, having a whole Great White Shark origin would require several other origins, and then half your movie is gone before you even have Batman appear.
How I'd do it: If the script called for a crooked rich guy from out of town, I'd name him Warren White as an easter egg for fans. That's about as far as I'd go for White.
Casting Guesses: I forget what White looked like before his ordeal in Arkham, but it seems like a role I'd want Steve Buscemi for. Sort of a supervillainous Mr. Pink.
Verdict: Almost certainly not. He's a very new and very unknown villain. The only chance is for dropping his name as an easter egg, but even that seems remote.
After The Scarecrow, Ra's Al Ghul, The Joker, and Two-Face, who should be Batman's next enemy in the Batman Begins/The Dark Knight series? Well, as of now we know that Tom Hardy will play Bane and Anne Hathaway will play Catwoman.
Check out the master list for all the villains covered. I've pretty much run out by now. Obviously, there are more Batman villains, but not any of significance that I know of. As of February 2009, no one is confirmed as a villain. Not the Johnny Depp Riddler, not Phillip Seymour Hoffman Penguin, nobody.