@stonecropsister: If you have just added this theme in your old site then first you need to regenerate thumbnails using plugin Regenerate Thumbnail. It’s mentioned in theme instructions page at http://catchthemes.com/theme-instructions/catch-evolution/
Then, as per Catch Evolution Free version, The header image is supposed to be changing with the featured image of post/page. Only in Pro version you have option to make it different or same.
If you want same image to display in all page, maybe you want to try uploading image as logo from “Appearance => Theme Options => Header Options”.
But if you want to use header image and want same header image to show in all pages/posts then you need to build child theme. For child them check out http://catchthemes.com/blog/create-child-theme-wordpress/. Then add the following function in you child theme functions.php
file
function catchevolution_featured_header() {
global $_wp_default_headers;
// Header Image
$header_image_path = get_header_image();
if ( get_header_image() ) : ?>
<div id="header-image">
<img src="<?php header_image(); ?>" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="" />
</div>
<?php endif;
}