Could you post them again in thumbnail size- the size they'd be on Goodreads or Amazon/B&N? I think a book cover should look good in the size where most people are likely to encounter them. If you think about it, only rarely are books in a library or bookstore shelved "face out"- covers showing. I think I like the third one best, but think it might be too busy in a smaller size.
Ooooh I like this cover I think its my favourite, very mysterious!!!!!
The third is my favorite! :)
The bottom one is my favorite.