For speed, performance, and templates.

1) In header.inc.php add a static url variable and update static content to use this url. By default just make it use the same URL as SiteURL. This would make it a very easy to setup a cookie less domain to provide static content AND would be serving content from multiple domains to increase number of connections to downloads of files. This new URL could also point to an origin pull CDN. That 'one' change could see a big improvement in three common test see more areas of page load test systems like Yslow.

2) Let google host jquery (and other large scripts) for us. Should be easy to add a jquery URL variable to header.inc.php as well as the static URL so people can easily use a local copy if needed for some reason. http://encosia.com/2008/12/10/3-reasons-why-you-should-let-google-host-jquery-for-you/

3) CSS Sprites. All the big sites use them. Show the template makers the right way to make a template load fast. If you combine 20 image (and requests to the server) in to one, you will see a speed up in page load time and a reduction of server resources. The down side to this is it would make it harder for swap out template images, but it is still possible to do by using a new sprite or custom images, or editing the old sprite and staying within the bounds of the sub image you need to change.