We all know that the search engines can't 'see' or 'read' the graphics on our pages. We also know that we need to provide text on a page, so the spiders will have something to crawl and index.
After all, we have to prove to the search engines without a shadow of a doubt that our pages are about what we say or claim they're about if we want to achieve top rankings. That's why I believe so strongly in focusing each page on one single keyword phrase only. As soon as a spider hits a page, I want the spider to know exactly what that page is about.
But, many sites out there are graphic intense, often by virtue of their very nature. The sites may sell prints, wallpaper, pictures, graphics, or posters. Or, the sites may sell hats, for example, so that each page is full of pictures of a particular type of hat.