Funtions.php

//* Add new image sizes
add_image_size('grid-thumbnail', 536, 150, TRUE);
add_action ( 'genesis_entry_header', 'sk_show_featured_image_home' );
function sk_show_featured_image_home() {
	if ( is_front_page() && has_post_thumbnail() ) {
		echo '<div class="home-thumbnail">' . '<a href="'.get_permalink().'">';
		genesis_image( array( 'size' => 'grid-thumbnail' ) );
		echo '</a></div>';
	}
}