Currently there's no way to use [list] without any symbol (which is useful for indents). You're teased to do something like this...
...but that will render invalid HTML (as <ul> doesn't allow plain character data and expects a surrounding <li> at least).
So I suggest to also use the type none for lists. To do so, only 2 files need to be modified:
Open /includes/bbcode.php and find
Open /includes/message_parser.php and find
Furthermore CSS2 types should be allowed. For these the function bbcode_list in /includes/bbcode.php needs to be augmented with more ELSE IFs for