How to get to a specific position in wp_query?

Question

Background:

I'm trying to display images in a slideshow, and I want to select those pictures randomly from the website's media. The image has a custom field in order to be selected for being the slideshow.

I was able to figure all of that out, and I used a wp_query to find all of the images with the custom field that says it could be used in the slideshow.

Question:

Now my problem is how should I go about looping through the query to get to the post number I want?

Code:

$args = array(
   'post_type' => 'attachment',
   'meta_key' => 'on_front_page',
   'meta_value' => '1'
);
$wp_query = new WP_Query($args);
$total_images = (int) $wp_query->found_posts;
if ($total_image >= 6) {
    for ($i = 0; $i < 6; $i++) {
        rand(0, $total_images);
    }
} 
elseif ($total_image >= 6) {
    for ($i = 0; $i < $total_image; $i++) {
       rand(0, $total_images);
   }
 }

Answer 1

I think instead of using PHP rand you're better off limiting ( if you need to ) using posts_per_page and then getting a random set using orderby => 'rand'.

Full List of Ordering Parameters

So if I were to edit your query it would look like this:

$args = array(
   'post_type'  => 'attachment',
   'meta_key'   => 'on_front_page',
   'meta_value' => '1'
   'orderby'    => 'rand'
   'posts_per_page' => 6
);

$slides = new WP_Query($args);
$total_images = (int) $slides->found_posts;

if( $slides->have_posts() ) {
    while( $slides->have_posts() ) {
        echo $post->ID;  // The Attachment ID
    }
}