Just to bring out a single point in derek's last reply. You shouldn't actually be using images, whether surrounded by divs or other elements, as layout images within the XHTML document... if you're aiming for separation of content from design.

If you're wanting a specific hook to apply CSS styles to display an image for the layout, then that's fine but use an empty div with an id attribute, rather than embed the image in the document.

Also, you're confusing (or at least blurring) the divide between standards and best practices. Nowhere does it say that anyone must use heading (or div) elements to display the website's name, just that it is a logical (practical) thing to do.