I used marcovidor’s solution
<div class="banner">
<?php if(get_post_meta($post->ID, 'banner', true)) : ?>
<img src="<?php echo get_post_meta($post->ID, 'banner', true); ?>" />
<?php else : ?>
<?php the_title(); ?>
<?php endif; ?>
<div>
and with some hacking (had to erase a default header that my theme got built in to the functions.php file & adapt widths of the header) got it to work great!