Images do more than just spice up your web pages. They act as page identifiers.
Users will recall the images that appear on particular pages of your website, and will use these images to identify these pages when they come back to your site, in much the same way that you might flip through a book and look for particular images in order to locate certain pages.
Images can — and should — be used as a way to illustrate the information that is being conveyed. For example, the image above might be used to identify a page containing product measurements.
Photographs of specific people should always have a caption below the image that contains the name of that person.
Images should also be identified with appropriate alt tags titles. Avoid using vague terms to describe the image. Try to be specific as possible.