Document usage of background instead of list-style-image for unordered lists

To reproduce:

Use default installation of Drupal 6.14, notably, using the Garland theme.

In a custom developed module mymodule.module, add a CSS file mymodule.css:

function mymodule_init() {
  drupal_add_css(drupal_get_path('module', 'mymodule') .'/mymodule.css');
}

In the custom CSS file, you want to have list without any bullet points. (Actually, setting any other list-style-type will also trigger this bug).

ul.mymodule {
  list-style-type: none;
}
ul.mymodule li {
  list-style-type: none;
}

Then output HTML from your module that is a UL list:

<ul class="mymodule">
  <li>This list item should have no bullet point at all.</li>
</ul>

Expected result

A list with no bullet point (or whatever you set with list-style-type).

Actual (wrong) result

The list still has a circle type of bullet point.

The bug is...

...in the default Garland theme, garland/style.css, different types of list markers are set using the background property:

Line 123:
ul li, ul.menu li, .item-list ul li, li.leaf {
  padding: 0 0 .2em 1.5em;
  list-style-type: none;
  list-style-image: none;
  background: transparent url(images/menu-leaf.gif) no-repeat 1px .35em; /* LTR */
}

(There are several others, for other selectors/classes.)

Using the background property for this purpose is very confusing. If I want to set my own bullet type I expect to set it with list-style-type. But doing that will not override the circle set by Garland.

How to correct this

Garland should use list-style-type or list-style-image for setting list bullets (the latter for images) as this is the expected way. background should not be used for this purpose.

Workaround

The desired effect is achieved by also setting background property in mymodule.css:

ul.mymodule {
  list-style-type: none;
}
ul.mymodule li {
  list-style-type: none;
  background: none;
}