This is the pattern that I feel the strongest about, but have the least empirical evidence for, and find the most disagreement with. I HATE going to sites with too many extraneous images. I load at 14.4 bps; I have to wait a long time for images to load; this site here makes me wait for their photograph of a willow tree with the links penciled attractively on the leaves, there are all these other sites that I want to visit and I COULD HAVE NAVIGATED THROUGH THIS SITE'S DOCUMENTS JUST AS EASILY, AND MORE QUICKLY, WITH STRAIGHT TEXT!
Is it just me?
In general, people don't pick up books, thumb through them, and say "I'm not reading this, there aren't any pictures!"; yet I've encountered that reaction over and over again when discussing the Web. In a book, if pictures are necessary, they are used. If they aren't necessary, they aren't used. Why is the Web different?
It is true that I could turn automatic image loading off in my browser, but there are other reasons not to use extraneous images. A minor reason is that the icons that represent graphics look really ugly for those of us loading at 14.4 bps who turn off auto-image loading. A more important reason is bandwidth.
Is it well-understood that bandwidth is a finite resource? A 256-color full-sized image of the cover of a hardcover book takes more time and space to transmit then the text of the entire book. I read somewhere (this is non-substantiated, if you can substantiate it or contradict it, please tell me) that when the Shoemaker-Levy comet crashed into Jupiter, the Internet was brought to a severe slowdown by the mass downloading of pictures of the comet; this situation could get worse as more and more people join the net.
I'm not condemning all the uses of images by any means. Images are absolutely necessary in a large percentage of Web documents: pictures can be used to illustrate a point or to tell a story, art students want to be able to show their talents in electronic portfolios, and VRML is a wonderful, low-bandwidth method of delivering complex images. But at a lot of sites, the images seem extraneous.
On the other hand, I may be completely wrong about this. A poll (somewhere on the Web; sorry, I'll add a reference later) showed that something like 80% of the Web users who took the poll preferred lots of images. I'd love to know what you think.
Therefore, IMHO,
Question the use of all images on your Web site. If the image conveys information that couldn't easily be conveyed via straight text, or if it is presented as a piece of art to be viewed, or if it is a low-bandwidth image or VRML description, or if it otherwise adds to the functional pattern language of the site, then use the image. Otherwise, consider using text instead.