Thanks, what if I wanted to do it with repeater rows? So…
<?php while ( have_rows('image_gallery') ) : the_row(); ?>
<div class="col-md-6">
<div style="background-image: url(<?php the_sub_field('image'); ?>); background-size: cover; height: 240px;">
<a href="#" style="display: block; height: 240px;"> </a>
</div>
</div>
<?php endwhile; ?>