Featured image showing in header - possible?

Hi there,

Love the theme - have managed to insert a logo instead of the title, but am trying to show the featured image in the header.

This is what I've added to the header.php sub-template:

<?php
if(has_post_thumbnail()){
echo '<div class="other-image-header">';
the_post_thumbnail('full');
echo '</div>';
}
else{
echo '<div class="default-image-header"></div>';
}
?>

and put this in various.css:

.default-image-header {
display: block;
width: 404px;
height: 202px;
background: url("%tpldir%/images/home.png");
}

.other-image-header {
width: 404px;
height: 202px;
}



Yet, for some reason I just can't get "the_post_thumbnail" to display, despite trying various iterations. Would love some advice on where I'm going wrong, or even a pointer in the right direction?