How to put images in the select tag in Asp-net core?

Question

<select>
  <option background="https://lipis.github.io/flag-icon-css/flags/4x3/gb.svg">gb</option>
  <option background="https://lipis.github.io/flag-icon-css/flags/4x3/pt.svg">pt</option>
</select>

<!-------Versão em .net core ------>
<form id="selectLanguage" asp-controller="Home" asp-action="SetLanguage" asp-route-returnUrl="@returnUrl" method="post" class="form-horizontal" role="form">
  <select name="culture" onchange="this.form.submit();" asp-for="@requestCulture.RequestCulture.UICulture.Name" asp-items="cultureItems"></select>
</form>

In the background I wanted the images to appear in this select