If I had seen the cover but never known anything about the book, I probably would have read it for the cover's sake alone. It's stunning and unexpected, and it makes me wonder what's going on. Why is her hair white? What's coming out of her mouth? Etc., etc. I just wish I knew, after reading the book, who it was.
I agree completely. The cover is absolutely beautiful, and I think it stands out. I know it popped for me on the shelf of the bookstore when I bought it.
Also, I think I agree with happyman that it may have been a suggestion by Vasher. But there was that one line I think where he says to Susebron "I'm the reason your tongue was cut out." Or something like that, right?