Here are a few of the mock-ups I've done to help me stay motivated just so you have an idea what I'm talking about (or don't follow me on FB).
This is a designed I built solely from a title, and by the time I was finished with the design an entire mysteries series had developed from it. Obviously inspired by seedy, sleazy 60s crime novels, this one will feature a lady of the 80s who gets drawn into the underbelly of city life in Atlanta.
A man holds up the office of a private detective. Why? I don't know yet, but when I do, it'll be because this mock-up has been constantly playing in the background of my brain.
This one will feature a serial killer who specializes in neo-burlesque dancers. Clearly a fetishist at work.
This one will be for a line of "Extreme" line of crime novels, all pretty clearly inspired by sleazy 60s pulps. Boy meets girl. High school ends. Boy becomes detective. Girl becomes hooker. Girls gets killed. Boy owes her this one and must solve the crime.
And to answer your question, yes. I've heard it lots of times: "Why waste time on those when you could be actually writing the book instead?"
That's actually a darn good question, but I think I have a darn good answer for it.
1. It creates an image that will rekindle the inspiration later when I'm ready for that book. Just looking at it again will bring all those feelings of excitement I had initially about the concept, and it will also remind me of the plot ideas I was playing around with in the pre-pre-pre-pre-writing phase.
2. It helps me practice the design side of my brain. It's a different way to think about a story, image rather than verbal, and that keeps my brain exercised and more trained for I sit down to write.
3. It keeps me motivated. I never have to ask, "What can I possibly work on now?" because I have a ready-made project eagerly awaiting my attention.
But... before you completely turn your nose up at the idea, why not give it a shot and see if it helps? You might be surprised the kind of ideas that releasing some visual creativity can give you.
There are lots of great resources online so you don't have to pay for expensive design software. Serif Drawplus is one, and so is Inkscape. Both of those are vector based (meaning anything other than the bitmapped images can be scaled up or down without loss of quality). For more traditional free image software, both PaintNet and Gimp are favorites of mine. All four of those can be downloaded and run offline. If you're looking for something you can do online for free, try either Canva or SVG-Edit.
If you decide to give it a shot, send me some of your mock-ups, and I'll share them in a future post here on the blog. Happy mocking up... er, mockupping... er, playing with fake book covers!