Yeah, Tilda Swinton she'd be one of my top picks. Mad acting chops, and she always comes off as incredibly creepy.
Cate Blanchett could be good, but I question her villain chops, after Indiana Jones 4.
I think a strong contender would also be Lena Headey, after seeing her in Dredd.
Charlize Theron also has the acting chops, given she won an Oscar for a portrayal of a female serial killer.
You want an actress who's distinctive looking, but not in a pretty way - I would find Kate Winslet too pretty, and Jessica Alba just doesn't have the acting chops for the role.
Eva Green could probably pull it off, but she's just too damn hot.
She's a bit past it now, but 15 years ago Glenn Close would have been the number one pick, no questions asked.