The InsertSmiley plugin allows the user to add Smileys by dialog.
Adding More Smileys
It is easy to add more smileys, in the plugins/InsertSmiley/smileys/ folder you will see all the smiley images, add more smiley images in this folder, then you can edit the smileys.js file in that same folder to "hook them up".
If your server supports PHP, you don't even need to edit the file, just make this Xinha configuration
xinha_config.InsertSmiley.smileys = _editor_url + '/plugins/InsertSmiley/smileys/smileys.php';
and it will automatically detect the new smileys.