query_tax for all images in posts

I see that there are numerable forum threads where people discuss getting all the images from a single post.

In this case I am trying to:

1. query for all posts that have a certain taxonomy ( in this case: projects )
2. then show all of the attached images from ALL these posts in a slideshow

This is what I have so far, which so far is only successful in getting the post_thumbnail:

<!-- featured slides for the projects -->
<ul id="featured_slides" class="rslides">
<?php

		 $related_project_posts = array(
		 'posts_per_page' => -1,
		 'post_type' => 'post',
		 'nopaging' => true,
		 'suppress_filters' => false, // this argument is required for CPT-onomies	

			'tax_query' => array(
			 	array(
		 	'taxonomy'=>'projects',
			'terms'    => get_the_ID(),
			'field' => 'slug'
			)),
		 );

//		print_r($related_project_posts);
$postslist = get_posts( $related_project_posts );
foreach ($postslist as $post) :  setup_postdata($post); ?> 

<li><a href="<?php the_permalink();?>"><?php the_post_thumbnail( 'grid_16_landscape' ); ?></a></li>
<?php endforeach; ?>
</ul><!-- featured_slides grid_16 //-->