I'm not able to find the image to modify
I don't find (2 hours of search :-) from where to change this background image.... argh!
See: http://noiliberali.enricocosta.it/wp-content/uploads/2015/09/Schermata.png
See: http://noiliberali.enricocosta.it/wp-content/uploads/2015/09/Schermata.png
Comments
this background image can be changed under Theme options > Custom CSS & JS > Custom CSS section. Below css is responsible for that background:
.contact_form {
background: rgba(0, 0, 0, 0) url("http://betheme.muffingroupsc.netdna-cdn.com/be/play/wp-content/uploads/2015/02/home_play_form_bgd.jpg") repeat scroll left top;
border-radius: 8px;
padding: 20px;
text-shadow: 3px 4px 4px rgba(0, 0, 0, 0.3);
}