Seems alot of hard work for something so basic…
Why not just simply do this to your header element in the header.php…
<?php if(is_page('About')) : ?>class="aboutpageclass"<?php else : ?>class="normalclass"<?php endif;?>
Which simply switches a class on a element, usage would be like so..
Example element..
<div id="header">
With code added..
<div id="header" <?php if(is_page('About')) : ?>class="aboutpageclass"<?php else : ?>class="normalclass"<?php endif;?>>
Then in your CSS apply style to the necessary classes, following the example above, something like….
Example..
.aboutpageclass { background-image:someimage.jpg; }
.normalclass { background-image:anotherimage.jpg }
Why go through the work of creating a template/page and fiddling with function calls when it’s such a simple and straight-forward task. Not saying the above is ‘wrong’ per say, but i don’t think it need be that much work…