I have already posted why you should hire a professional cover designer for your ebook, here is how I chose mine. I did try to create my own cover for my first ebook, ‘The Railway Angel’ (perma-free on most platforms), but got as far as choosing the background photo and that was it. I had no idea about layouts, fonts etc. Smashwords was fairly new then, and I had already printed out their formatting guidelines to use. Back then, on the website, you had to email a blank email to an address to Mark Coker, and he would send you a list of formatters and designers. I got this list, and went through it to find someone who had designed covers for YA fantasy. I found her, and checked out her website. Seeing the covers she had designed, and that they were similar to what I had in mind, I noted her name and email address for when I chose the right photos. Her name is Joleene Naylor and like most of the designers on that list, she lives in the US. She no longer takes new clients.
The list of formatters and designers can now be found at this link http://www.smashwords.com/list
So, if you need to pay for a professional cover designer, choose one that does covers for the same genre that you write. If you like what they do for you, then keep with them. I have stayed with mine, and am happy with what she has done and will do for me. And she charges a reasonable rate.