Try this
$wp_query = new WP_Query( array(
'post_type' => 'post',
'posts_per_page' => -1,
'meta_key' => 'delight_image',
'meta_query' => array(
'relation' => 'AND',
array(
'key' => 'delight_image',
'compare' => 'EXISTS',
),
array(
'key' => 'delight_image',
'value' => array(''),
'compare' => 'NOT IN',
),
),
) );
It’s from something I found here http://wordpress.stackexchange.com/questions/10881/how-can-i-show-posts-only-if-meta-value-is-not-empty