I’m glad to hear you figured out the image ID issue. This is probably the biggest thing that trips up people when they first start using the snippets. We have thought about different ways to address this but haven’t come up with a solution we are happy with.
For anybody else that runs into image issues using the snippets, the IDs in the example snippets are from our own demo site. You will need to change the image IDs to match IDs for your own images.
The quickest way to find an image ID is to use the image shortcode dialog and choose an image as if you were going to use the shortcode. This will put the ID into the image field.
You can also find the IDs by looking at the URLs of the edit image links in the media library.