Getting post thumbnail URL

I haven’t tested this, but you might be able to use this (or something like it…):

$url = wp_get_attachment_url( get_post_thumbnail_id($post->ID) );
<img src="<?php echo $url; ?>" longdesc="URL_2" alt="Text_2" />

http://codex.wordpress.org/Function_Reference/get_post_thumbnail_id
http://codex.wordpress.org/Function_Reference/wp_get_attachment_url

Maybe this then?

<?php $thumb = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), 'thumbnail_size' );
$url = $thumb['0']; ?>

http://codex.wordpress.org/Function_Reference/wp_get_attachment_image_src

oops, I forgot to specificially mention that thumbnail_size should be the name of the thumbnail size you’re using (I think the default is ‘post-thumbnail’?) – did you try swapping that out?

Here is where the the_post_thumbnail() function is defined, you might be able to follow the trail: http://phpxref.com/xref/wordpress/wp-includes/post-thumbnail-template.php.source.html#l40

glad you got things working out

Worked for me, thanks. Below is how I used it in it’s entirety – just in case anyone wants a quick C’nP.

<?php query_posts('category_name=Portfolio&order=ASC&orderby=date&posts_per_page=36'); ?>

<?php if (have_posts()) : ?>
<?php while (have_posts()) : the_post(); ?>

<?php
$thumb = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), 'thumbnail' );
$url = $thumb['0'];
?>
<li><a style="background-image:url(<?=$url?>);" href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"></a></li>

<?php endwhile; ?>
<?php endif; ?>

@Chozen Can you post what code you have so far? If it’s lengthy, please use something like http://pastebin.com/.