Add custom field on Contact-Us form

For italian law, we need to add a simple checkbox (required) in foot section of "contact-us" form. This is for "privacy compliance"

Like:

[ ] I have read and understood the privacy policy on the processing of personal data and the use of cookies, thus authorize the use of my personal data pursuant to Legislative Decree 196/2003

How can we add it ?

u can use all in one plug in
http://www.hezyziv.com/all-in-one

just paste in html and  javascript code and it will be shown on the contact page
set the widget zone to: "contactus_bottom"

<script type="text/javascript">
                    $(document).ready(function () {
                        $('.contact-us-button').click(function () {
                            //terms of service
                            var termOfServiceOk = true;
                            if ($('#termsofservice').length > 0) {
                                //terms of service element exists
                                if (!$('#termsofservice').is(':checked')) {
                                    $("#terms-of-service-warning-box").dialog();
                                    termOfServiceOk = false;
                                } else {
                                    termOfServiceOk = true;
                                }
                            }
                            if (termOfServiceOk) {
                                //$('#confirm-order-form').submit();
                                //$('.confirm-order-next-step-button').attr('disabled', 'disabled');
                                return true;
                            } else {
                                return false;
                            }
                        });
                    });
                </script>

<div id="terms-of-service-warning-box" title="@T("Checkout.TermsOfService")" style="display:none;">
                        <p>@T("Checkout.TermsOfService.PleaseAccept")</p>
                    </div>
                    <div class="terms-of-service">
                        <input id="termsofservice" type="checkbox" name="termsofservice" />
                        <span>@T("Checkout.TermsOfService.IAccept")<a class="read" onclick="javascript:OpenWindow('@Url.RouteUrl("TopicPopup", new { SystemName = "conditionsofuse" })', 450, 500, true)">@T("Checkout.TermsOfService.Read")</a></span>
                    </div>
                    }
                    <div class="buttons">
                        <input type="submit" name="nextstep" value="@T("Checkout.ConfirmButton")" class="button-1 confirm-order-next-step-button" />
                    </div>

Is There any way, I can attach an image and submit to database by script?