body {
margin: 0;
display: flex;
justify-content: center;
background: url('your-image') no-repeat center center;
background-size: cover;
}
#wrapper {
width: 60%;
}
#header {
padding: 20px;
text-align: center;
background: transparent;
}
#main {
display: flex;
}
#content
width: 60%;
}
#sidebar {
width: 40%;
}
#content, #sidebar {
padding: 20px;
display: flex;
flex-direction: column;
}
.titlebar {
height: 40px;
background: url('your-image') no-repeat center center;
background-size: cover;
}

<div id="wrapper">
<div id="header">big title</div>
<div id="main">
<div id="content">
<div class="titlebar">your menu here</div>
<div>perhaps use iframes here to easily change content using the menu</div>
</div>
<div id="sidebar">
<div class="titlebar"></div>
<div>your guestbook iframe</div>
<div class="titlebar"></div>
<div>your stamps</div>
</div>
</div>
</div>