I have done that with my blog - http://www.sheilamckayphotography.wordpress.com -
this is the css I used
body {
color:#00000;
background:#ffffff;
font-family:Arial, Helvetica, sans-serif;
font-size:75%;
line-height:1.6em;
text-align:center;
margin:0;
padding:15px 0;
}
body#commentspopup {
background:white;
padding:0;
}
h1,h1 a,h2,h2 a,h3 a,h4 a {
color:#CC0000;
}
h1 a:hover,h2 a:hover,h3 a:hover,h4 a:hover {
color:#A2CD5A;
}
a {
color:#00000;
text-decoration:none;
}
a:hover {
color:#A2CD5A;
}
a.commentlink {
padding-left:16px;
background:url('images/spring_flavour/comments.gif') center left no-repeat;
}
a.more {
padding-right:10px;
background:url('images/spring_flavour/more.gif') center right no-repeat;
}
pre,code {
background-color:#A2CD5A;
}
kbr {
color:#A2CD5A;
}
#container {
border-top:0 solid white;
background:url('images/spring_flavour/container_bg.gif') 500px 0 repeat-y;
width:1024px;
text-align:justify;
margin:0 auto;
padding:25px 30px 0;
}
#container.singlecol,#commentspopup #container {
background-image:none;
}
#header {
background-color:#ffffff;
background-image:url('http://farm3.static.flickr.com/2736/4404463603_19e36d87c2_o.jpg');
height:450px;
padding:0;
}
The only thing I changed was the ('http://. . . . . . . . . . . jpg') to change the image but the header is very small although I did not change anything else.
This was the new image I was trying to change:
http://farm5.static.flickr.com/4106/4958544489_f0c98549f2.jpg
Thanks so much for your help.