>> BTW: if you want a >really< interesting background, then use an animated gif
>
> Uh, what?
>

You know that gifs can be animated. This, aside from being reliably transparent in any browser, is the main attraction of this format. And any image, even an animated one, can be displayed as background.

I once designed a backgound for a bathroom shop which would display ascending bubbles on a blue background by first creating a seamlessly tileable background and then animating the bubbles into a gif. Seven years ago this was a nice way to animate an intro-screen... but since I got paid for it I cannot post it.

So I quickly cooked up a small ani: after 4s it will chage colours, do this 4 times, then stop changing for the rest of the session.

Try making a webpage with the attached image as background.

Maybe your newsreader will show it, too, though I would not rely on this.