i have psd design with background image that width is only 940px;
what i going to do ?

tell the designer that is work going to work only in small screen that see only 940px width ;

i try this:
background: url(img/header.jpg) no-repeat center center fixed;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;

but is only work on big images;

here the psd design:


what you guys do when you come up with design that is width is only 940px ?