replaces the review widget title with an attachment image if one is provided

product_reviews_pro_replace_title_image.php

/**
 * Replace contribution titles with the contribution image
 *
 * NOTE: requires version higher than 1.6.3 to use this filter
 *
 * @param string $title the contribution title
 * @param \WC_Contribution $contribution the contribution object with comment data
 * @return string - updated title
 */
function sv_wc_prp_replace_widget_contribution_title( $title, $contribution ) {
	echo '<img src="'. $contribution->get_attachment_url() .'">';
}
add_filter( 'wc_product_reviews_pro_widget_contribution_title', 'sv_wc_prp_replace_widget_contribution_title', 10, 2 );