This is/was a challenging title for your first cover here, so don't let it get you down if the process isn't immediately successful.
Your best bet starting out would probably be to choose a title with great resources available, just to get used to filling the canvas.
With that said, if you use the poster Jazzy posted, and maybe add the title in white, that could look quite nice.
The spine doesn't have to be a perfect extension of the front if the image isn't conducive. For example, on your current cover the dark blue text is difficult to read, so a plain blue or a different simple sky piece might work better for you.
For the back, if you fix the image proportions as Speedz0r suggests and have the synopsis fill out the entire width so you don't have to worry about the block of blank space on the top-right, that could be a very respectable result. Maybe even darken the blue shape a little to match the front.
Depending on the image quality, the result still might not quite qualify to upload here, but it would be great practice so that your second cover will be even better.
