BUT ALSO CAN'T FIND it here on the site, whether I've posted my uberpost on book cover design. (Confirmed: I haven't. It's still sitting here as an unfinished draft. And it will remain so. No time to finish. Not this weekend.) But life goes on, and here comes one Patrick Samphire, from Wales, with some tips for self-publishers designing their own covers.
Now, you should Read The Whole Thing (RTWT), without doubt, as it's all good advice, but I'd like to focus briefly on one point, because I think it bears a little discussion.
Unless you're a Photoshop professional (and by this I mean someone who uses Photoshop to make a living, every day; using Photoshop at home or occasionally at work doesn't count), then don't attempt to make an image using multiple source photos. It will look bad, and it will be obvious.
Compositing photos, particularly if you've first had to extract part of one image from a background, is really, really hard to do well enough. Even some commercial covers suffer from bad attempts at this.
Find a single piece of art or photo that works and use that.
I don't generally approve of appeals to authority. You can do it. You should be able to figure it out. The capabilities are not dark, mysterious, or rare, precious, and beautiful. They are a matter of knack crossed with obsession. Somebody with some slight innate ability works at a skill until it becomes second nature.
However, even then, there will be a certain portion of fooling around as a part of the creative process.
What Samphire says makes sense from a business standpoint.
In my work, handling the work of other world class artists and designers, I see people whose names you should recognize make the rookie mistakes that Samphire is talking about.
I do work in Photoshop daily. Have done for longer than some of you have been alive well over 20 years. I know it well enough that I can assess an image and explain to someone else how to perform the actions I envision. I did peer support on CompuServe for Adobe back in the '90s. I contributed to the Photoshop Bible. If you know anything about bitmap editing software, you have some notion of what all that means.
I am here to tell you that, despite my faith in your ability to learn, you don't have the time to pick up what I know in my mouse fingers about image manipulation in Photoshop. Your work will look bush league, your sales will suffer, you'll waste your time. Listen to the man when he tells you: not.
Hire a pro or set the bar lower.