This is pretty difficult, but can be done by adding this custom css:
.extraclass .sf-icon-box-animated .front {
background-image: url("http://dante.swiftideas.net/wp-content/uploads/2012/09/jb_cute_monster-770x404.jpg");
background-repeat: no-repeat;
background-size: 100% auto;
padding-top: 150px;
padding-bottom: 15px;
}
.extraclass .sf-icon-box-animated i {
display: none;
}
You will need to create extra classes for each icon box, then add the class to the extra class field.
You will need to replace the background image to the url of your image, and you may also need to edit the padding.
– Kyle