add_shortcode( 'show_members', 'show_members_cb' );
function show_members_cb( $atts ) {
    $atts = shortcode_atts(
        array(
            'id' => 0
        ),
        $atts
    );
    if( $atts['id'] == 0 ) {
        return 'You need to provide a membership ID';
    }
    $args = array(
        'membership_id' => $atts['id'],
        'subscription_status' => 'active'
    );
    $members = MS_Model_Member::get_members( $args );
    $html = '<table cellpadding="5" cellspacing="5">';
        $html .= '<tr>';
			$html .= '<th>Thumb</th>';
            $html .= '<th>First Name</th>';
            $html .= '<th>Last Name</th>';
			$html .= '<th>County</th>';
        $html .= '</tr>';
    foreach( $members as $member ) {
        $html .= '<tr>';
            $html .= '<td>' . get_avatar( $member->id ) . '</td>';
            $html .= '<td>' . $member->first_name . '</td>';
            $html .= '<td>' . $member->last_name . '</td>';
			$html .= '<td>' . get_cimyFieldValue( $member->id, 'county' ) . '</td>';
        $html .= '</tr>';
    }
    $html .= '</table>';
    return $html;
}