It’s quite easy to make a striking cover. There are some talented artists around and there are also some very good stock pictures available, which you can download for a small fee and use more times than you’d probably be able to sell books.
However, getting the cover to look right isn’t just a matter of having a fabulous picture. You need to take several other matters into account:
Is there a natural place for the lettering?
Or the blurb?
What colour / shape should these be if they are to show up well?
Will the size of the book allow you to have a decent–sized spine? One where you can fit in the title and the author?
Will the picture bleed okay without losing integrity?
Will the paper version be a good match to what you see on screen? This point can be very vexing. Printers produce colour in a very different way from computer screens. Printers who know what they are doing can make the paper version match the digital file but they can’t guarantee that they can match what you are seeing on your own computer screen. You need to set your screen to industry standards and it’s actually not quite possible with domestic screens and totally impossible with laptops.
You also have to remember that a colour will look much darker on mass than it does in small quantities in the lettering – especially if letters are against a dark background.Be prepared to be surprised. If you’re using a professional designer, they tend to know what they’re doing, so the surprise can be a pleasant one. You may have a few nasty shocks if you’re doing it yourself. Even so, try to look at that cover objectively. Does it actually work? Does it matter that it doesn’t look exactly as you saw it on your screen? As long as you’ve actually not got any nasty clashes it could be fine.