Thanks dogoodzilla,
which lines do I have to remove from the header? I’m not a complete expert at php so sometimes I don’t quite get it right!
<?php
// Check if this is a post or page, if it has a thumbnail, and if it's a big one
if ( is_singular() && current_theme_supports( 'post-thumbnails' ) &&
has_post_thumbnail( $post->ID ) &&
( /* $src, $width, $height */ $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'post-thumbnail' ) ) &&
$image[1] >= HEADER_IMAGE_WIDTH ) :
// Houston, we have a new header image!
echo get_the_post_thumbnail( $post->ID );
elseif ( get_header_image() ) : ?>
But I must’ve got that wrong as the header wouldn’t load anymore…
Thanks!