This can be done by setting the choices to images, for example
1 : <img src="/wp-content/uploads/2017/05/image1.jpg" />
2 : <img src="/wp-content/uploads/2017/05/image2.jpg" />
You can also use other html, for example <i class="fa fa-address-book"></i>
You can even use an acf/load_field filter if you want to set the images dynamically.