A 3D graphic representation of a book, a folder, file, etc., is known as an "E-Book cover". These images are often utilized by authors, marketers and publishers of E-Books and other non-physical ("intangible") products such as emails newsletters, report downloads, membership web sites, etc.
There are many possibilities for how you could use these images. Here are a few ideas:
1. You could use the image to jazz up your web site.
2. You could use the image as part of the header graphic on your site.
3. If you offer a range of multiple products, you could allow users to choose between them, by clicking on the corresponding E-Book cover graphics. However, since it can be hard for visitors to read text on tiny images, I recommend that in addition to the graphics you also provide a method of navigating using text links, or some explanatory text, or, at very least, some mouseover text for each graphic.
4. If you create your own products, you can use the cover within the product itself. For example, you could incorporate the graphic in the first page, in the About page / screen, in documentation, headers / footers, etc.
5. If you use an E-Book compiler such as Activ E-Book Compiler that supports the splash screens images, you could use your cover for the splash image.
6. You could use the graphic in advertising creatives. For example you could use the cover graphic itself, or incorporated within a banner graphic.
7. If you promote other people's E-Books (for example because you are an affiliate), you could create covers for them, and use those covers as part of your marketing efforts. Note: It's both wise and polite to ask permission from the E-Book seller before doing this.
8. You could start a service creating E-Book covers for others. You can either sell the covers that you create, or you could trade them for something else that you want – for example, links to your web site.