I just encountered this problem too, and your first answer led me to a tighter solution.
I also used types_render_field(), but if you include a 'raw' parameter, you can avoid the string manipulation.
$images_raw = types_render_field('image', array('raw'=>'true','separator'=>';'));
$images = explode(';', $images_raw);
foreach ($images as $link) {
echo '<a href="' . $link . '" class="fancybox" rel="gallery">' . $link . '"></a>"';
}
Then, if you're nasty, you can get the ID of the attachment from its SRC. Using that ID, you can get all the info you need about that attachment, like a caption, or whatnot.