wpquestions.com, ID = 2961

<?php // First Image Loop

$args=array(
    'post_type' => 'animals',
    'orderby' => 'rand',
    'posts_per_page' => 7
);

$i = 0; // set counter at 0
$query = new WP_Query($args);

while($query->have_posts()) : $query->the_post();

    // different code for each image based on the counter
    switch ($i) {
        case 0:
            echo "first image - {$post->ID}";
            break;
        case 1:
            echo "second image - {$post->ID}";
            break;
        case 2:
            echo "third image - {$post->ID}";
            break;
    }

    $i++ // increment counter

endwhile;

?>