For a cover the first one is your best choice because it makes better use of empty space. Also the orange helps it a ton. If I were printing this I'd love to do that image with two spot colors for the yellow and orange, rather than a 4-color process print, to give it a nice and striking screen printed look. Number 6 is also nice, but you need more space up top for the title, or you'll have to set it on a title bar to separate it from the background.

Is the image supposed to be wraparound? Because these are all very horizontal designs for just a front cover (assuming you've got the more traditional portrait proportions for the book).

Also your title design could use some tweaking. It's hard to make multiple fonts look unified, so you've set a big challenge for yourself there, you might consider eliminating one of them and using just two typefaces rather. (I assume you've got aesthetic reasons for the choices, but I mostly associate this kind of type design with deliberately retro soap packaging and the Ringling Bros.) The weighting of the words is off, you've got a heavier font on "The" than on the far more significant "City." Maybe try a really small (almost like superscript style) "The," and a narrower "Unknown" to bring its width closer to that of "Fabulous."