.nav {
    display: block;
    width: 100px;
    height: 30px;
}

.nav.home {
    background-image: url(images/Home.png);
}
.nav.home:hover {
    background-image: url(images/Homehover.png);
}

.nav.foo {
    background-image: url(images/Foo.png);
}
.nav.foo:hover {
    background-image: url(images/Foohover.png);
}