How to show next Post Thumbnail image in WordPress using current post id

Here is the template layout and code for your original question. I am using wp_get_recent_posts as it gives me recent posts from the category as you wanted, if not change orderby to rand for random posts, as wp_get_recent_posts return posts by default in array form you can also have a choice to shuffle them.

I checked your answer its not consistent and too much replication of codes as your first post uses rst-postpic and than rst-postinfo and so on, instead of this use post type or some meta field to determine the type of post and according to that print information about post.

Hope it helps and gives you an idea to proceed further.

Happy coding!

<?php
    $args = array(
         'numberposts' =>    6,
         'category'    =>    0,
         'post_status' =>    'publish',
         'orderby'     =>    'post_date',
    );
    $recent_post = wp_get_recent_posts( $args );

    //shuffle( $recent_post );    // Just for randomness
?>
<div class="row">
    <div class="col-xs-12">
        <div class="rst-mediagrid">
            <?php
                 foreach ($recent_post as $key => $value) {
                     $class_col_50    =   $key == 0 || $key == count( $recent_post ) - 1 ? ' rst-col-50' : ' rst-col-25';
                     $class_col_video =   $key % 3 == 1 ? ' rst-postvideo' : '';

                     if ( $key % 3 === 0 )
                         echo '<div class="div">';

                     echo "<div class="rst-col$class">";
                         echo "<div class="rst-postpic$class_col_video">";
                             echo  $value['ID'], ' ';
                         echo '</div>';
                     echo '</div>';

                     if ( $key % 3 === 2 )
                         echo '<div class="clear"></div></div>';
                 }
            ?>
        </div>
    </div>
</div>