[WooCommerce Currency Converter Widgets] Using country flags instead of country codes.
a[data-currencycode="USD"] {
background-image: url('http://upload.wikimedia.org/wikipedia/en/a/a4/Flag_of_the_United_States.svg') !important;
background-size: 60px !important;
width: 30px;
background-repeat: no-repeat;
font-size: 0;
height: 20px;
}