Pull URL from Custom Field on a page without repetition

My home page has an image which populates via a URL inserted into the custom field I’ve created. My snippet of code is displaying my img tag 3 times, first 2 with no src, (i.e. <img src with=900>), and the 3rd properly. It even eliminats the equals sign and the 2 double quotes. This is the snippet I am referring to:

<main id="home">
	<?php query_posts('post_type=page'); ?>
	<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
    	<img id="showcase" src="<?php echo get_post_meta($post->ID, 'Main Home Page Image',true); ?>" width="900">
	<?php endwhile; ?>
        <?php else : ?>
        <h2>Not Found</h2>
	<?php endif; ?>
        <?php wp_reset_query(); ?>
    </main>

When this renders in the browser, I get 2 blank squares and the 3rd is the image I want. Source code when rendered looks like this:

<img id="showcase" src width="900">
<img id="showcase" src width="900">
<img id="showcase" src="http://localhost/wp-content/uploads/2014/04/index.jpg" width="900">

I am simply looking to pull the URL once and have it populate the image. Again, this is coming from a page not a post. Can anyone offer me some insight?