I'm afraid that no, you can't put your own HTML in place of the banner image in the template.

The best you could easily do is to make an Animated GIF and use that as your banner image. Or you could perhaps do a "hack" whereby

We are currently working on some new HTML5 themes which we hope will be available in the not too distant future (our designer is currently working on making some pretty layouts). These will be prettier and more modern, and work well on mobile devices, as well as being more flexible in what you can do with the layout of the page. (though even with the new themes, I don't think it'll be possible for you to use your own HTML in the base template).

Thanks

Joe - Voice Admin