Definitely the fourth one.
i like the lettering on the first one best, but the design of the fourth one best. i do think it would be cool if you layered the fourth cover with an echo of the yellow outline over the solid black of the sillohuette staggered to the side just a bit to add some depth to the design...but you know your story and style best, of course! also, just wanted to say that i think the lettering is fantabulous, and if you go with at different title, i hope you still keep that lettering style!
the last one is the only one which is eye catching, the rest are too dark and do not draw attention. But I would change fonts at that one. And make them bigger as well. Is there a connection between the woman's body and the title and the story?
I'll agree that the lettering on the first one and the design of the fourth one are the best options here. However, the coloring of the first's letters wouldn't work well with the fourth. The color of the gold letters wouldn't mesh very well with the yellow background of the fourth. Perhaps if their colors can be brought to a better blend, or complete contrasts? I understand the need for that gold lettering, though, as a visual representation of the Steampunk ideal. Maybe the background could be from the contrasting side of the palette? I'm behind a firewall right now that has everything blocked, but if you look up the Moses Harris Color Wheel from 1776 (or a more modern one, if you prefer), you'll get an idea of the opposing colors. Yellows tend to pair up with purples. An example: Do a search for orange and blue movie posters. You'll see The Bourne Identity, Fantastic Four, Stardust, The Last Airbender, The Dark Knight, GI Joe, The Taking of Pelham 123, Tron, Star Trek. All of these -- while some may not be great movies -- had successful marketing campaigns specifically because the orange and blue posters popped. Not in the traditional sense of "popping," but the opposing colors triggered something in the visual cortex that drew the eye to the poster. I guess what I'm saying is perhaps the gold lettering of Steampunk from number one can be used with the image on number four, but the background could lean more toward the indigo/purple/blue on the color wheel? The only other note I would add is that the embossed outline of the first three caught my eye, and I wonder if that sort of little detail could be added to the outline of the arm/wrist/hip/side of the fourth. Just enough to make it stand out from the background; like she's coming off the cover/about to reach through the screen and take your hand.I'd say that was my two cents, but it's probably worth closer to eight. For what it's worth.Also, I'd like to see this when you're done with it. I'm a big fan of steampunk.