Create an easy guide to show how HTML markers can be used to achieve this, possibly create a CSS class specifically designed for this to make it easy to implement for those that have access to the functionality.
This request will start an endless stream of "More and more pins" request, I will bet. Also for any icon / symbol / letter that has not a convenient map pin, you could use the Html Special Pins - those are able to use ANY symbole, FontAwesome and RPG Awesome symbole - AND can be styled with the already existing CSS class to look like the map pins. Yes I am aware, CSS Is a Guild Member Functionality.