Core has 4 css classes for the flags Dutch, French, German and English. Because these languages are quite often used. You can use these classes on buttons in Actions or Views.
<i class="ems-flag-xs-nl"></i>
<i class="ems-flag-sm-fr"></i>
<i class="ems-flag-md-de"></i>
<i class="ems-flag-lg-en"></i>