Dynamic Slider Image from Custom Post

 Example One

<?php if(!is_paged()) { ?>

<?php

$args = array( 'post_type' => 'slider-items', 'posts_per_page' => 6 );

$loop = new WP_Query( $args );

?>  

<?php while ( $loop->have_posts() ) : $loop->the_post(); ?>

<div class="pc_item"> 

<?php the_post_thumbnail('slider-image'); ?>

</div>

<?php endwhile; ?>

<?php wp_reset_query(); ?>

<?php } ?>

OR
<?php if(!is_paged()) { ?>
<?php
$args = array( 'post_type' => 'slider', 'posts_per_page' => 4 );
$loop = new WP_Query( $args );
?>
<?php while ( $loop->have_posts() ) : $loop->the_post(); ?>
<li>
<?php the_post_thumbnail('slider-image', array('class' => 'postthumbnails')); ?>
</li>
<?php endwhile; ?>
<?php wp_reset_query(); ?>
<?php } ?>

Example Two

   <ul class="slides">

<?php
global $post;
$args = array( 'posts_per_page' => 4, 'post_type'=> 'slider-items');
$myposts = get_posts( $args );
foreach( $myposts as $post ) : setup_postdata($post); ?>

<?php $slider_image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'slider-thumb' ); ?>
<li data-thumb="<?php echo $slider_image[0]; ?>">
<?php the_post_thumbnail('slider-larger'); ?>
<?php the_content(); ?>
</li>
<?php endforeach; ?>

</ul>