Certainly there are many ways to dynamically change the page background. Although current trends in webdesign suggest the use of small amounts of special effects, however, sometimes use a simple slideshow in the background, you can beautify the look of the website.
Main Funsupersized Features
- Resizes images to fill browser while maintaining image dimension ratio
- Displaying unlimited slide images
- Cycles backgrounds via slideshow with transitions and dynamic preloading
- Core version is available for those that just want background resizing
- Navigation controls with keyboard support
- Performance options
If you are using WordPress you should check out WP Supersized developed by Ben De Boeck.
Almost this same features have new module Spoton Imaging Big Screen (code.google.com/p/spoton-imaging/) is another a browser-based full screen background slideshow. This extension is compatible with Joomla 1.5, 1.6, and 1.7
By the way, as you probably know Joomla’s templates generally have the same background style for each and every page. By applying HD-Background Selector (http://www.hyde-design.co.uk/free-joomla-extensions/hd-background-selector) – module to a specific page the background can be styled individually from the others, increasing the variety of your design without resorting to using multiple templates. This simple module that allows you to apply a different background style to individual pages on your Joomla website. You can select background colours, images or repeated patterns. It can be applied to the main background or to specific elements (eg. module positions, columns, headers, footers, main content box, etc) on your site. By default the module replaces the style applied to the “body” tag.