Using an image for header in Wordpress, CSS still needed?

If i use an image for a header for a Wordpress theme am i correct in believing that i still then use CSS for dimensions/positioning of the header.

For example including the image with something like the following:

#header {
background: #73a0c5 url('images/kubrickheader.jpg') no-repeat bottom center;
}

But then i still use CSS along with that for width, height, margin setting?

Feel free to correct me if neccessary please.

 

As long as the header is still wrapped in that style, you can do this.

 

Thanks markn26