Just look for this code of wp-content/plugins/private-messages-for-wordpress/inc/send-page.php
<?php wp_editor( $content, ‘rw-text-editor’, $settings = array( ‘textarea_name’ => ‘content’) );?>
and change it for this one
<?php wp_editor( $content, ‘rw-text-editor’, $settings = array( ‘textarea_name’ => ‘content’, ‘media_buttons’ => false ) );?>
