When you present your images for sale, consider using gallery features that allow you to group your images into categories based upon similarities. For example, I have a gallery that is dedicated only to unusual geology, and another that is just for water shots. You can set up a gallery for images with a dominant blue color theme, or for photographs from a specific location. Your options are wide open.
We use SmugMug for our online print sales, and I absolutely love the Smart Galleries feature. It lets you use keywords to create collections, so that potential buyers view images with shared characteristics. When a buyer wants more than one image, they often have a theme in mind. One buyer asked me for 30 detail shots that she could sell as a wallpaper collection. Another wanted several waterfall photographs for decorating a newly opened hospital. In Cleveland, a buyer wanted images of local parks and iconic locations for the walls in an office building. As you build your portfolio, keep an eye out for images that work well together, and be sure to present them as potential groupings.