This add-on makes it possible to set custom icons for each node. For forums and categories you can set read and unread node icons, for pages and links only one icon because they do not have unread state.
Add-on uses Iconify icon picker to show selection of over 30,000 icons.
To find icons similar to chat bubbles search for following phrases:
Screenshot of nodes list with custom node icons:
Screenshots of admin page:
To set custom icons edit node in admin panel. You will see new option to set custom icons for read and unread node. Make sure you set both, otherwise XenForo will show default icon.
This add-on is in beta. It has been tested only with default style. If it does not work correctly with your style, please post about it in this add-on's discussion thread.