You have to add your parameters to the FormData object (using append) and as always pass the formdata object alone as the data property.
$('#id_image').on('change', function () {
var currentpath = window.location.pathname;
var formData = new FormData($('form')[0]);
formData.append('csrfmiddlewaretoken', '{{ csrf_token }}');
$.ajax({
url: currentpath, //server script to process data
type: 'POST',
data: formData,
cache: false,
contentType: false,
processData: false
});
});