Reuse a class styles and append to multiple classes e.g. template styles as a base for a class.
%bg-image {
width: 100%;
background-position: center center;
background-size: cover;
background-repeat: no-repeat;
}
.image-one, .image-two {
@extend %bg-image;
}
.image-one {
background-image:url(/img/image-one.jpg");
}
.image-two {
background-image:url(/img/image-two.jpg");
}