If you can use the HTML5 File API and the FormData Object.
var xhr = new XMLHttpRequest();
xhr.upload.addEventListener('progress',function(ev){
console.log((ev.loaded/ev.total)+'%');
}, false);
xhr.onreadystatechange = function(ev){
// Blah blah blah, you know how to make AJAX requests
};
xhr.open('POST', url, true);
var files = document.getElementById('logo').files;
var data = new FormData();
for(var i = 0; i < files.length; i++) data.append('file'+i, files[i]);
xhr.send(data);
You can do data.append('name', document.getElementById('name')) etc. to append all the other form fields.