EDIT: I finally got the right answer; see my own answer beneath this post for everyone that's interested.
After searching for a couple of days and trying over and over again I really got stuck. I've a client who collects customer experiences on his website by using the comment form; all comments are displayed as a customer review. So far so good.
But since it's company does a lot with traveling, he needs to give his customers to upload up to five images with there review.
So what I need to do is find a way to let customers upload media along with there filled in comment form. I do know it's kind of risky, since there could be corrupt images uploaded and so on. But still, I would like to achieve it.
Tried a lot a things but the point where I get stuck over and over again is the file upload handling, for a non-logged-in user which is posted with a comment form...
Any thoughts will be very appreciated!