I figured it out. Here is my code…
<section>
<?php
$args = array(
'orderby' => 'name',
'order' => 'ASC'
);
$categories = get_categories('child_of=39', $args);
foreach($categories as $category) { ?>
<div class="casino-games">
<?php $image_url=get_field('featured_category_image', $category); ?>
<a href="<?php get_category_link( $category->term_id ) ?>" title="<?php sprintf( __( "View all posts in %s" ), $category->name ) ?>" />
<h3><?php echo $category->name ?></h3>
<img src="<?php echo $image_url ?>" /> </a> </div>
<?php } ?>
<div class="clear"></div>
</section>
it was this part that did the trick for me…
<?php $image_url=get_field('featured_category_image', $category); ?>
