ACF | Type: PHPACF Random Image Repeater

<?php 
  //must select ImageID as Return Value
	$rows = get_field('title_images' ); // get all the rows
	$rand_row = array_rand($rows, 1); // get a random row
	$rand_row_image = $rand_row['img_title']; // get the sub field value 

	$titleimage = wp_get_attachment_image_src( $rand_row_image, 'full' );
	// url = $image[0];
	// width = $image[1];
	// height = $image[2];
?>

<header class="hero" style="background-image: url(<?php echo $titleimage[0]; ?>)">
</header>

Reference Links

https://support.advancedcustomfields.com/forums/topic/random-image-repeater/