Hi Diego,
You can solve this by editing the file /ClientScript/tiny_mce3392/plugins/emotions/js/emotions.js
Change this line:
src : tinyMCEPopup.getWindowArg('plugin_url') + '/img/' + file,
like this:
src : ed.getParam( 'emotions_images_url', tinyMCEPopup.getWindowArg('plugin_url') + '/img/' ) + file,
Thanks for pointing this out.
Best,
Joe