I had an annoying usability problem with Advanced Custom Fields. Users of the system did not understand how to change or remove an already uploaded image, because the buttons to do so only show up after the user has hovered over the existing image, like this:
Here is a little snippet that you can add to your functions.php file in your theme to always display these buttons in the admin.
add_action('admin_footer', function()
{
?>
<style type="text/css">
.acf-image-uploader .hover
{
visibility: visible;
opacity: 1;
}
</style>
<?php
}, 999);