functions.php

<?php

//----------------------------------------------------------
// Display Posts Shortcode plugin: add H2 to title
//----------------------------------------------------------
add_filter( 'display_posts_shortcode_output', 'format_dps_title', 10, 9 );
function format_dps_title( $output, $original_atts, $image, $title, $date, $excerpt, $inner_wrapper, $content, $class ) {

	// Make Title and H2
	$title = ' <h3>'. $title .'</h3>';

	// Now let's rebuild the output.
	$output = '<' . $inner_wrapper . ' class="' . implode( ' ', $class ) . '">' . $image . $title . $date . $author . $category_display_text . $excerpt . $content . '</' . $inner_wrapper . '>';

	// Finally we'll return the modified output
	return $output;
}