change header

i would like to kknow if i can change the header which is just one colour to in image? and if so how i can do this
thanks

In <template folder>/css/template_css.php you have this:

.header {
background-color:<?php echo $headerBg; ?>;
}

change it something like:

.header {
/*background-color:<?php echo $headerBg; ?>;*/
background: URL(image url) ...
}