I redesigned the book cover for Fishy Fall. I can do it for about $5. Just purchase a royalty free picture from a site online. I use bigstockphoto.com, drop the photo into my word document - using the insert photo tab. Add my text - then take a picture of what's on my computer screen with a little gadget I got for free, an app through snapa shot. Voila! Instant cover.
Granted it's not like Salty Summer, but it's the best I can do right now.
The covers I create work great on Amazon.com so long as they are 500w x 800h (pixels). For some reason when I take a snapa shot it reduces the number of pixels. Barnes and Noble has higher resolution requirements. I just talked to a local print shop, Roxy told me she could increase the digital resolution of all four book covers for $30 by using her special software. So I will have that done and get my book covers posted on Barnes and Noble. You can manipulate pictures at home if you have the right software ... which I don't. Barnes and Noble requires 750w x 1000h with a resolution of 72 dpi.
All that techno mumbo jumbo means you're better off buying a good quality picture to start with, probably medium size. On bigstock that's $4.99. Play around with different text options until you've developed your own personal style for your cover.