there are 2 changes  in joomla 1.5 templates! the fist is Template can able to carry parameters .the second is can Editable multiple template css.

Template is able to carry parameters

In Joomla! 1.5 templates are able to have parameters just like modules. This new feature is extremely powerful as it allows developers to create super flexible and versatile templates. All parameters and operation related to template are located in new page Template Parameters.

• Here from toolbar we can all template operations such as editing HTML and CSS code, preview, save and apply.
• In field "Details" we see all information about the template.
• In Joomla! 1.5 templates are able to carry parameter like modules. By adding this feature we can now expect a lot more flexible and usable templates.
• Here in field "Menu Assignment" we can assign template to particular menu item. However there are 2 types templates you can't do assignment: Administrator templates and Default Site template

Editable multiple template css

As we all remember in Joomla! 1.0 template could use multiple CSS files, but from Joomla! Administration we could edit only the default "template_css.css". Now in Joomla! 1.5, we can edit all CSS files used by the template.To edit desired CSS file, we just need to click radio button near it and click Edit button on the toolbar.