A /motif-powered template can have an unlimited number of non-core themes. A non-core theme is any theme in the /themes folder that is not named "core" or "mobilecore".
To create a non-core theme, the first thing you need to do is add a new folder to the /themes folder. The name of this new folder will be the name of your theme. Any file you add to this theme will be used instead of its counterpart in the core theme when this theme is set as the primary theme. For example, if you add a file named "index.php", this file will be used instead of the core theme's index.php file. If you do not add an index.php file, the core theme's index.php file will be used by default.
To add CSS files, create a /css folder and simply add CSS files. If the CSS file you add has the same name as a CSS file in the core theme, this file will override the core theme's CSS file. If you add a CSS file that does not have the same name as a CSS file in the core theme, this file will be loaded after the core theme's CSS files.
Javascript files work the same as CSS files. To add Javascript files, create a /js folder and simply add Javascript files. The same override functionality that CSS files use applies to Javascript files.
