Here is my page where I will refresh my CSS skills
Fontawesome
Fontawesome is a cool tool to add icons to your page. Drupal has a module to add the icons. You can add the icon button to the ckeditor toolbar in the editor.
From the W3Schools website there are a number of additional icon "producers" like Google Icons and Bootstrap Icons that I have not used. Were I to explore using them I would look and see if there were Drupal modules to add them.
Here is me playing around with a link. First I add a class to it to make it a unique button and then I add psuedo classes to it in order to get it to act in different ways.
Cool, isn't it.
Interesting thoughts.