You should really look into the background size property instead of using fixed images. Using 'cover' for background-size, means that the image should grow or shrink just enough to cover the whole background.
If you know the dimensions of the image. You can use a media query to change the background-size to 'auto' when it would otherwise grow beyond it's original size.
html, body {
min-height: 100%;
}
body {
background-image: url(http://leydenlewis.com/images/LANDING_PAGE.jpg);
background-repeat: no-repeat;
background-position: 0 0;
background-size: cover;
}
@media (min-width: 1120px), (min-height: 630px) {
body { background-size: auto; }
}