JSFiddle - React, Tailwind, and code Playground

HTML

<div class="combo">
    <span class="flag-it"></span>
        <select>
            <option value="Italiano" selected>Italiano</option>
            <option value="English">English</option>
            <option value="Français">Français</option>
            <option value="Español">Español</option>
            <option value="Nederlands">Nederlands</option>
    </select>
</div>

CSS

body {background: palegoldenrod;}
.combo {
    background: silver;
    margin: 10px 0;
    position: relative;
}

.combo span {
//    display: block; float: left;
    width: 16px; height: 11px;
//    margin-right: 10px;
    background: white url('flags.png') no-repeat;
//    line-height: 1;
    position: absolute;
    top: 50%;
    margin-top: -5.5px;
}

.combo select {
//    vertical-align:middle;
//    line-height: 1;
    margin-left: 26px; // 16px + 10px
}

.combo span.flag-es {background-position: -16px 0}
.combo span.flag-fr {background-position: -32px 0}
.combo span.flag-gb {background-position: 0 -11px}
.combo span.flag-it {background-position: -16px -11px}
.combo span.flag-nl {background-position: -32px -11px}