multiple background images using CSS

Is it possible to have two background images? For instance, I’d like to have one image repeat across the top (repeat-x), and another repeat across the entire page (repeat), where the one across the entire page is behind the one which repeats across the top.

I’ve found that I can achieve the desired effect for two background images by setting the background of html and body:

html {
    background: url(images/bg.png);
}

body {
    background: url(images/bgtop.png) repeat-x;
}

Is this "good" CSS? Is there a better method? And what if I wanted three or more background images?