WordPress CSS head info – contents, expansions?

There is no reason to add something not listed in WP_Theme class $file_headers array because it simply will not be recognized.

private static $file_headers = array(
        'Name'        => 'Theme Name',
        'ThemeURI'    => 'Theme URI',
        'Description' => 'Description',
        'Author'      => 'Author',
        'AuthorURI'   => 'Author URI',
        'Version'     => 'Version',
        'Template'    => 'Template',
        'Status'      => 'Status',
        'Tags'        => 'Tags',
        'TextDomain'  => 'Text Domain',
        'DomainPath'  => 'Domain Path',
);