To be able to include anything other than text in the timeline and avoid the Loading problem, edit WORDPRESS_ROOT/wp-content/plugins/wp-veriteco-timeline/wp-veriteco-timeline.php, replacing line 360:
$string .= stripslashes($entry->toJSON());
$string .= $entry->toJSON();
Optional but recommended step: update TimelineJS code. Download the latest TimelineJS code from here (2.25, as of this writing). Unzip it and copy everything under TimelineJS-VERSION/compiled/js/ to WORDPRESS_ROOT/wp-content/plugins/wp-veriteco-timeline/js/ and everything under TimelineJS-VERSION/compiled/css/ to WORDPRESS_ROOT/wp-content/plugins/wp-veriteco-timeline/css/. And that's it. This way your timeline will look just like the one at timeline.verite.co.
Tip: To pull media from Google Maps/Twitter/Flickr/SoundCloud/Vimeo/YouTube/Wikipedia/etc include a link to it in the Timeline Meta Data > Video Embed field of your post.