In this topic you can see how it is easy to extend MotoPress Content Editor library of visual objects. It allows to add your custom shortcodes to MotoPress Content Editor library, customize and remove existing ones. You can do that within the functions.php file of your theme or in your plugin.
To start and retrieve the library with existing visual objects you can use
add_action('mp_library', 'your_function_name', 10, 1);
// Create function with required input parameter - $motopressCELibrary
// all magic happens here