Font Awesome icons dropdown

I am working on symfony project and I want to add dropdown to a form. The dropdown should contain only icons without any text. I tried using select option like this:

<select class="form-control" name="category">
    <option value="">
        <a class="category-icon icon-bed"></a>
    </option>
    <option value="">
        <i class="fa fa-wrench fa-fw"></i>
    </option>
    <option value="">
        <i class="fa fa-wrench fa-fw"></i>
    </option>
</select>

But it doesn't show any icon. How can i do that? Thanks