One of my favorite authors had a few titles reissued. It was a medieval historical romance set in Scotland. So why were Texas bluebonnets gracing the cover? If I hadn't already been familiar with the book, I would have thought it was a western.
Another well known author did have a contemporary western set on a ranch outside Houston. Some editor, probably in New York, designed a cover of a cowboy riding his horse down a dirt road along side a ranch house with beautiful mountains in the distance. Huh? The nearest mountains are over six hundred miles west in Big Bend. These were obviously somewhere in Colorado.
I have to admit, I've put down a book because of cover models who look like teenagers. Who wants a hero who looks like he's fifteen? Even the guy who is prettier than the female model turns me off. Yeah, I know, everyone has their preference.
With e-publishing, you at least have a little control. Of course, a professional cover can cost quite a bit. Is it worth it? Readers are quirky. Many do judge a book by its cover.
Choose wisely, ask friends and critique partners, the hope for the best.