@k.capelli: You can add the css like the following CSS in “Appearance => Theme Options => Custom CSS” box to add your custom image in the header background.
#branding {
background: url("http://www.thelostlondoner.com/wp-content/uploads/2013/09/id1.jpg") repeat scroll 0 0 transparent;
}
For menu, it’s better you just add the background url from “Appearance => Theme Options => Color Options”. But if you really was to add image, then you can add the following CSS in “Appearance => Theme Options => Custom CSS” box, where you can just change the image url.
#access {
background: url("http://www.thelostlondoner.com/wp-content/uploads/2013/09/id1.jpg") repeat scroll 0 0 transparent;
}
To make the header center, you can add the following CSS in “Appearance => Theme Options => Custom CSS” box.
#branding .logo-wrap, #site-logo, #site-details {
width: 100%;
}
#site-logo a img, #site-details {
display: block;
float: none;
margin: 0 auto;
padding: 0;
text-align: center;
}
This is the level at max I can help in. For more, you need to hire developer to customize it for you.