A picture is worth a thousand words, and a good book cover is worth more!
There is more to book covers than just a picture and a title. To design a cover, one needs some technical know-how to understand the image sizes, color formats, and resolutions. Also, we need an element of artistic ability to understand how to make a cover that pleases to your audience.
When you are creating (or hiring to create) book covers, understand that print books, eBooks, and Audiobooks all have their own separate image sizes, so create a separate cover file for each format.