Load image from custom meta field

Version 3.0 introduced some hooks for manipulating the results. You can use the dwls_attachment_thumbnail filter to change what’s put in the thumbnail field. Off the top of my head, I think you just need to return the URL of an image you want to use.

Hi Dave, I like this plugin very much and I am trying to make it work thumbnails this filter adding something like this in function.php (on the end of file)

add_filter('dwls_attachment_thumbnail', 'dwls_test_attachment_thumbnail');
function dwls_test_attachment_thumbnail($foo) {

   get_the_post_thumbnail ($id, 'thumbnail', array('class' => 'photo main_photo'));

   echo get_the_post_thumbnail();

}

This is not working , so can you please give me advice about this ?
Thanks

Sorry for not getting back to you sooner. A filter needs to return the modified content. So in your case:

$foo = get_the_post_thumbnail();
return $foo;