Merging get_posts returned arrays

The best solution would be to separately query for all image attachments whose parents meet your criteria, orderby rand. You then have two big random arrays, one of posts, one of images. Then step through the arrays by index number using a counter that is incremented for each iteration of the loop, outputting a post and image each time.

The problem is I’m not sure you can construct such a query with WP_Query. You could do this using $wpdb methods, but I suck at writing SQL queries, so I can’t help you with that part ??

Alternately, you could work off what you already have. What would need to change is to not send output from the loop you have. The loop would simply accumulate all the images. To accumulate images, just add square brackets to $thumb, like so:
$thumb[] = wp_get_attachment_image($image->ID, 'thumb', false );

After the main post loop runs, randomize $thumb with shuffle($thumb); You now have two big random arrays just like you would have with the separate image query. Run another loop to output the content using an index counter the same way as previously mentioned.

Thanks bcworkz! I ended up using $wpdb methods. I’m terrible at SQL queries as well, but I got the shuffle to work. I’m now trying to get it to only return from the custom category. Once I get that part of the query, I’ll post the working code. This is the post that helped me get to where I currently am.

OK! Got it to work with some help from a friend who is skilled in SQL queries. Here’s the working code:

This runs at the top of the page to get the array values we will use in the SQL query:

<?php
				$catargs = array('taxonomy'=> 'custom-category');
				$categories = get_the_terms($post->ID, $catargs); // Global variable for terms
		?>

Here’s the magic query:

<?php

			$post_cat = $category->taxonomy; // This will equal a custom category type.
			$post_term = $category->term_id; // This will equal the page's category id.
				// Sets the global $wpdb
				global $wpdb;
				// Starts the db query
				$query = "
				SELECT DISTINCT ID, guid, post_parent FROM $wpdb->term_taxonomy, $wpdb->terms, $wpdb->posts p where p.post_type = 'attachment'
                                AND p.post_mime_type LIKE 'image/%'
                                AND p.post_status = 'inherit'
                                AND p.post_parent IN
                                        (SELECT object_id FROM $wpdb->term_relationships WHERE term_taxonomy_id = $post_term)
                                AND $wpdb->term_taxonomy.taxonomy = '$post_cat'
                                AND $wpdb->terms.term_id = $post_term
				";

			$results =  $wpdb->get_results( $query );

			if ( $results ) {
			shuffle($results);
  					foreach ( (array) $results as $image ) {
  						$url = get_attachment_link($image->post_parent);
  						$thumb = wp_get_attachment_image( $image->ID, 'thumbnail', false );
  						$alt = get_post_meta($image->ID, '_wp_attachment_image_alt', true);
  						echo '<li style="display:inline-block;"><a href="' . get_permalink($image->post_parent) .'">' . $thumb . '</a></li>'."\n";
  					}
				}
		?>

What this will do is return all images associated with a particular custom category ID.