Code Suggestions

This looks like a really promising tool! Very excited to use it more.

One thing I noticed: on line 698 where you drop in the URL for the link, I added a check for a flickr link so that site links open in a new window.

if ( ! empty( $url ) && $link == 'flickr' ) {
	echo '<a href="'. $url .'" target="_blank">';
} elseif ( ! empty( $url ) ) {
	echo '<a href="'. $url .'" >';
}

Seems like a better user experience on the front end.

https://wordpress.org/plugins/flickr-api/