Need help – CSS header & bg

Hi,
I was asking my self how I could change the background color and introduce an image as the header.
Here I copy the Css flie, maybe you can help me with it ??

*{
margin:0;
padding:0;
list-style:none;
}
body {
font: 70% “Lucida Grande”,”Lucida Sans Unicode”,geneva,verdana,sans-serif;
margin:10px;
color:#555;
}
html {
height: 100%;
margin-bottom: 1px;
}
.header {
background: #000;
cursor: pointer;
padding:4px;
}
#footer {
width:660px;
margin:0 auto;
color:#ccc;
}

#footer a {
color:#aaa;
text-decoration:none;
font-weight:bold;
}

#footer .validate {
float:right;
}

.header:hover{
background-color:#666;
}

#header h1 a {
color:#333;
text-decoration:none;
}

#header h1 a:hover {
color:#000;
}

Thx in advance (: