Sending $_FILES through JQuery

Sending $_FILES through JQuery

Hello

I'm doing a form which contains a gallery with PHP+MySQL. I'd like to add the possibility to upload images using jQuery in case of the image I'd like to use is not in the gallery. The problem is, $_FILES doesn't send through $.post.... I was reading and, as I understood, this is not possible. 

Another option would be open a pop-up window to upload the file. But in this case, when I go back to the form, the pictures must be updated with no reload it (because if I reload I miss all the information I have typed before). How could I do it?

In definitive, I'd like to add something like this: $('ul').append('<li><img src... /><span>NAME</span></li>'); to the main page form, when the popup window image is recorded.

Thank you