There is a new web artform that has arisen with the design and release of Outlook Express. I'm referring to Outlook Express Stationery. These stationery designs go way beyond the standard templates. They now include some absolutely brilliant artwork, sometimes scrolling, multiple overlays and embedded or streaming audio tracks.
I mention this medium here, as the format takes full advantages of the features you describe in this thread.
To view some great examples just key in Outlook Express Stationery on Yahoo and visit some of the sites. You'll be amazed.