Display featured image as background image?

I'd like to take a featured image and make it a background image.

I've attached a screen shot of what happens. When a featured image is in place, it takes over the entire box. What I would like to happen is the featured image is used as a background image.

Here is the code that is calling this in:

<article id="post-<?php the_ID() ?>" <?php post_class('popular-post') ?>>
	<?php if (has_post_thumbnail()) : ?>
		<a class="feature-img" href="<?php the_permalink() ?>"><?php the_post_thumbnail('feature-img'); ?></a>
	<?php else: ?>
		<div class="post-details">
			<?php printf('<div class="date-info">%s / <span class="time">%s</span></div>', get_the_date(), get_the_time()); ?>
			<a href="<?php the_permalink() ?>"><?php the_title('<h2 class="post-title">', '</h2>') ?></a>
		</div><!-- END POST DETAILS -->
	<?php endif; ?>
</article>

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Screen shot attached. Any help is appreciated.


Thanks.