Great concept so far. Of the helms, I really like the 5th one, the one with almost no one inside. Creepy! Can't choose a favorite thumbnail, though: They're all terrific and any one could work. Slight pref for the top middle one because of the dramatic upwards angle (though I'd suggest flipping it so he's facing right... but I suppose the current layout is better for a book cover. But they're all great. Good luck whichever you choose, and keep it coming!