If you can setup a field, then you can do something like:
<?php $image = get_field('image');
if( !empty( $image ) ): ?>
<img src="<?php echo esc_url($image['url']); ?>" alt="<?php echo esc_attr($image['alt']); ?>" />
<?php endif; ?>
You would need to change the field name from image to whatever you need.
Or you could do something like:
<?php $image = get_field('image');
if( !empty( $image ) ): ?>
<img src="<?php echo esc_url($image['url']); ?>" alt="<?php echo esc_attr($image['alt']); ?>" />
<?php else: ?>
<img src="url-to-placeholder" class="placeholder-class" ?>
<?php endif; ?>
That way you don’t need the jQuery, as it checks if an image exists/been added if not, uses a fall back to a placeholder image
