Link to full size post thumbnail

You have to do a small bit of magic to get the url with the correct size image:

$image_url = wp_get_attachment_image_src( get_post_thumbnail_id( $idx ), "size" );

You should put in the appropriate thumbnail size for “size” at the end, of course 🙂 Sounds like you’d want “full”.

Make this a variable in your while variables, then in your array, call something like:

'thumb-link' => $image_url[0]

(For posterity, the Codex reference for related info: http://codex.wordpress.org/Function_Reference/wp_get_attachment_image_src; sizes listed here: http://codex.wordpress.org/Post_Thumbnails)