Okay, so I've chosen the art for the cover. That's it, right?
Well... not quite yet.
(I just realized I should put a disclaimer here: I'm not a professional cover designer. That should be really obvious to anyone who knows what they're doing. I've picked up a few tricks along the way, but if you learn anything at all from this, it should be things that you want to think about in a cover, not things I've done.)
Okay, that's done with. Let's get back to this cover.
First off, it doesn't quite have the right dimensions. Here's what it looks like if I change the frame to be the right proportions:
One thing I should point out: the image has a nice slant from upper left to lower right, which will help draw the viewer's eye correctly (for English readers who read left-to-right, top-to-bottom — it's a whole thing and I'm sure there are articles about it. All I know is that I want an image that draws the eye about like this.). If the image hadn't already been positioned like this, I would have flipped it around to get it this way.