Cover design can range from the simplest where an image is placed on the cover of the book and text designed around it, to the most complex where unique artwork is created or a composite/montage of images are combined to create an overall image.
As a result, the cost can vary enormously.
Examples of simple graphics include the following:
An example of a composite montage made from a series of images is shown below. This was prepared from a client brief where the client asked for a city hall, a hill, a psychiatric facility, a woman being led away and a man. A lot of work but with the right graphic artist it can be done.
The childrens book below contained original illustrations taking in the key components of the story. An owl, a tree, a rainbow and a little bit of magic (the little light sparkles).
Non fiction books can be easier to design and it should be easy to tell what the book is about by its cover.
For example a travel guide may show a map, route or image of the area, a cookery book may show recipes, utensils, pictures of cooking, food styling etc.
Books used by business professionals may emphasize more the purpose of the book-its features and benefits. An example being a life coach may have a simple picture or graphic and supporting text for the Title or Title/Subtitle so that it will be clear what the book is about. Examples below show books in the self-help sector.
Consider also books that have no images just text. A key example being Dale Carnegie. His book titled How to Stop Worrying and Start Living-Time-Tested Methods For Conquering Worry contains a combination of blue, black and white font on a red, white and yellow background! No graphics yet it is crystal clear what the book is about.