Add a field to the taxonomy editor?

This is not Woocommerce specific, just the regular WordPress term edit screen. So you can use the normal action {$taxonomyname}_edit_form_fields.

Example:

add_action( "product_cat_edit_form_fields", function() {
    ?>
    <tr class="form-field">
        <th scope="row">Additional image</th>
        <td>Some image upload code …</td>
    </tr>
<?php
}, 2000 );