@lucabriganti85: Yes, I check in different screensizes and it’s only the issue with large screens which is not comment in Web browsing. So, this should be fine. If you try to increase the image size more then 1600px to support very large screen, then you will have loading issue. As I have already told you the web browser user of this screen size is less then 2%. So, you need to think about it.
Also there is one css trick that you can stretch this image for large screen by adding in the following css in “Appearance => Theme Options => Custom CSS” box:
#main-slider img {
width: 100%;
}