Out of the box the Tiris template has only the modules shown. In J2.5 most modules you can apply a background from the module manager. However, if you want something more customised to your needs then it is simply a matter of creating your own css and then using the suffix in your module.
Obviously, I cannot do that for you as I do not know what designs you want but there are plenty of tutorials around the web. Or you could look at the template.css files for other JA templates and see how those are created.
