ACF Repeater Random

<?php 

$rows = get_field('repeater_field_name' ); // get all the rows
$rand_row = $rows[ array_rand( $rows ) ]; // get a random row
$rand_row_image = $rand_row['sub_field_name' ]; // get the sub field value 

// Note
// $first_row_image = 123 (image ID)

$image = wp_get_attachment_image_src( $rand_row_image, 'full' );
// url = $image[0];
// width = $image[1];
// height = $image[2];
?>
<img src="<?php echo $image[0]; ?>" />