Displaying Posts output by Display Posts Shortcode in Masonry.

functions.php

//* Enqueue Google Fonts and JS script
add_action( 'wp_enqueue_scripts', 'magazine_enqueue_scripts' );
function magazine_enqueue_scripts() {

	wp_enqueue_style( 'google-fonts', '//fonts.googleapis.com/css?family=Roboto:300,400,700|Raleway:400,500,700,900', array(), CHILD_THEME_VERSION );

	// wp_enqueue_script( 'magazine-entry-date', get_bloginfo( 'stylesheet_directory' ) . '/js/entry-date.js', array( 'jquery' ), '1.0.0' );
	wp_enqueue_script( 'magazine-responsive-menu', get_stylesheet_directory_uri() . '/js/responsive-menu.js', array( 'jquery' ), '1.0.0', true );

	//* Enqueue Masonry
	wp_enqueue_script( 'masonry' );
	//* Initialize Masonry
	wp_enqueue_script( 'masonry-init', get_stylesheet_directory_uri() . '/js/masonry-init.js', array( 'masonry' ), '1.0.0', true );

}

//* Add new image size
add_image_size( 'masonry-thumb', 146, 0, true );

add_filter( 'display_posts_shortcode_author', 'sk_remove_by_author' );
/**
 * Remove 'by' before author name in Display Posts Shortcode output
 *
 * @author Sridhar Katakam
 * @link   http://sridharkatakam.com/
 */
function sk_remove_by_author( $author ) {
	$author = ' <span class="author">' . get_the_author() . '</span>';
	return $author;
}

add_filter( 'display_posts_shortcode_output', 'be_links_in_new_window', 20 );
/**
 * Add a target="_blank" to the anchor tag in posts output by Display Posts Shortcode
 *
 * @author Bill Erickson
 * @link   https://github.com/billerickson/display-posts-shortcode/wiki
 */
function be_links_in_new_window( $output ) {
	return str_replace( '<a ', '<a target="_blank" ', $output );
}

gistfile1.txt

[display-posts posts_per_page="10" include_author="true" image_size="masonry-thumb" meta_key="_thumbnail_id" wrapper="div" tag="se-policies"]

masonry-init.js

jQuery( function( $ ){

	var $container = $('.display-posts-listing');
	// initialize Masonry after all images have loaded  
	$container.imagesLoaded( function() {
	  $container.masonry({
	  	itemSelector: '.listing-item',
  		gutter: 5
	  });
	});

});

style.css

/* Masonry effect on Display Posts Shortcode
--------------------------------------------- */
 
.listing-item {
	border-radius: 0;
	width: 19.4666666667%; /* 146px via http://cl.ly/image/3g2V100s3Q3d */
	overflow: hidden;
	background: #ddd;
	margin-bottom: 5px;
}

.listing-item a img {
	vertical-align: top;
}

.listing-item a.title {
	display: block;
	padding: 10px;
	color: #000;
	line-height: 1.3;
	font-weight: 700;
	font-family: 'Raleway', sans-serif;
	word-wrap: break-word;
}

.listing-item a.title:hover {
	color: #f41d00;
}

.listing-item .author {
	padding: 10px;
	font-style: italic;
	font-size: 15px;
	line-height: 1.3;
	display: inline-block;
	font-family: 'Roboto', sans-serif;
}

@media only screen and (max-width: 1024px) {
	.listing-item {
		width: 24.375%;
	}
}

@media only screen and (max-width: 768px) {
	.listing-item {
		width: 19.4366197183%;
	}
}

@media only screen and (max-width: 568px) {
	.listing-item {
		width: 24.2661448141%;
	}
}

@media only screen and (max-width: 480px) {
	.listing-item {
		width: 32.5617283951%;
	}
}

@media only screen and (max-width: 320px) {
	.listing-item {
		width: 49.1319444444%;
	}
}