its not on a image,
create a header.php & footer.php
inside header.php put all your header content, well everything that is above your site MAIN content.
inside footer.php put all your footer content, well everything that is below your site MAIN content.
than creat a index.php and organize it like this :
CODE
<?php include("header.php"); ?>
Your Main Content Here
<?php include("footer.php"); ?>
what it does is that it saves header.php and footer.php so when ever you hit a page (change page) it actually only loads the MAIN content.
So there is a cache, it doesnt load your images all the time, and the site is much faster, but there are other ways to load your site faster :
i saw you had some blank images, (images of ONE color) instead of puting a link of your images put a background color, your site will load a bg color faster than an image. even if its a 10x10 coz imagine you have many pics like this... it'll save some more time...
also the file type such as gif, png, jpg, bmp, ... look for the lowest !