Create a slider from current gallery images of each post in the featured content slider.

gistfile1.php

<?php
add_filter( 'tgmsp_slider_images', 'tgm_custom_gallery_images', 100, 2 );
function tgm_custom_gallery_images( $images, $meta ) {

  // If the Featured Content Addon is not active, return early.
	if ( ! class_exists( 'Tgmsp_FC' ) )
		return $images;

	// Go ahead and get image attachment size.
	if ( isset( $meta['custom'] ) && $meta['custom'] )
		$size = $meta['custom'];
	else
		$size = 'full';

	// Re-apply the query args from the featured slider.
	$pid   = wp_get_post_parent_id( $images[0]['id'] );
	$posts = get_posts( Tgmsp_FC_Shortcode::get_instance()->query_args( array(), $pid ) );
	if ( $posts ) :
		$current_gallery_images = array();
		foreach ( (array) $posts as $post ) :
			$attachments = get_posts( array( 'post_parent' => $post->ID, 'post_type' => 'attachment', 'posts_per_page' => -1, 'post_status' => null, 'post_mime_type' => 'image', 'orderby' => 'menu_order', 'order' => 'DESC' ) );
			if ( $attachments ) :
				foreach( (array) $attachments as $attachment ) :
					$image = wp_get_attachment_image_src( $attachment->ID, $size );
					$data = apply_filters( 'tgmsp_image_data', array(
						'id' 		=> $attachment->ID,
						'src' 		=> $image[0],
						'width' 	=> $image[1],
						'height' 	=> $image[2],
						'title'		=> isset( $attachment->post_title )   ? $attachment->post_title   : '',
						'caption' 	=> isset( $attachment->post_excerpt ) ? $attachment->post_excerpt : ''
					), $attachment, $post->ID );
					$current_gallery_images[] = Tgmsp_FC_Shortcode::get_instance()->featured_image_data( $data, $attachment, $pid );
				endforeach;
			endif;
		endforeach;
	endif;

	return $current_gallery_images;

}