Web pages normally add images using the inline HTML "img" tag. CSS coding usually doesn't set an image's source because CSS controls design rather than content. Yet CSS supports properties that ...

The background-image and background-color properties should be used to add background images and colors to HTML elements, with a fallback color for email clients that do not support background images.

Google says images styled with CSS won’t be indexed in Image Search, advising developers to use HTML tags for important visuals.

images/ ) to that graphic. This is the only property required in order to place an image in the background. Note that, unlike HTML, the CSS code doesn’t use quotation marks in its path to the image.