Custom field for image, not showing image!

It looks like you’re using a custom plugin. Is that the case?

Anyway for the line:
<?php echo get_post_meta($post->ID, 'banner_image', true); ?>

Why aren’t you using something like:

<img src="https://wordpress.stackexchange.com/questions/21729/<?php bloginfo("template_url'); ?>/images/<?php echo get_post_meta($post->ID, 'banner_image', true); ?>"/>

Another way to debug is to echo the post ID to the screen and see if it is indeed 49. Let us know what’s going on.