Using new Media Uploader in Option Tree for gallery. Credits for idea how to handle it to shibashake.com. Thanks!

functions.php

<?php
function ot_type_puregallery( $args = array() ) {
    /* turns arguments array into variables */
    extract( $args );
    global $post;

    $current_post_id = $post->ID;

    /* verify a description */
    $has_desc = $field_desc ? true : false;

    /* format setting outer wrapper */
    echo '<div class="format-setting type-post_attachments_checkbox type-checkbox ' . ( $has_desc ? 'has-desc' : 'no-desc' ) . '">';

    /* description */
    echo $has_desc ? '<div class="description">' . htmlspecialchars_decode( $field_desc ) . ' <br/><a href="#" class="delete-gallery">Delete gallery</a></div>' : '';

    /* format setting inner wrapper */
    echo '<div class="format-setting-inner">';

    /* setup the post types */
    $post_type = isset( $field_post_type ) ? explode( ',', $field_post_type ) : array( 'post' );
    global $pagenow;
    if($pagenow == 'themes.php' ) {
        $args = array(
            'post_type' => 'attachment',
            'post_status' => 'inherit',
            'post_mime_type' => 'image',
            'post__in' => explode( ",", $field_value),
            'posts_per_page' => '-1',
            'orderby' => 'post__in'
            );
    } else {
        $args = array(
            'post_type' => 'attachment',
            'post_status' => 'inherit',
            'post__in' => explode( ",", $field_value),
            'post_mime_type' => 'image',
            'posts_per_page' => '-1',
            'orderby' => 'post__in'
            );
    }

    /* query posts array */
    $query = new WP_Query( $args  );

    /* has posts */ echo '<input type="hidden" name="' . esc_attr( $field_name ) . '" id="' . esc_attr( $field_id ) . '" value="' . esc_attr( $field_value ) . '" class="widefat option-tree-ui-input ' . esc_attr( $field_class ) . '" />';
    if ( $query->have_posts() ) {
        echo '<ul style="margin:0px" id="option-tree-gallery-list">';
            while ( $query->have_posts() ) {
                $query->the_post();
                echo '<li>';
                $thumbnail = wp_get_attachment_image_src( $query->post->ID, 'thumbnail');
                echo '<img  src="' . $thumbnail[0] . '" width="60" height="60" />';
                echo '</li>';

            }
        echo "</ul>";
        echo '<a title="Add images" class="option-tree-attachments-update option-tree-ui-button blue right hug-right addgallery" href="#">Edit Slider Gallery</a>';

    } else {
        echo '<ul style="margin:0px" id="option-tree-gallery-list"></ul><p>' . __( 'No Gallery', 'option-tree' ) . '</p>';
        echo '<a title="Add images" class="option-tree-attachments-update option-tree-ui-button blue right hug-right addgallery" href="#">Create Slider Gallery</a>';
    }

    echo '</div>';

    echo '</div>';
}
//fake and dirty shortcode for stupid media uploader
function media_view_settings($settings, $post ) {
    if (!is_object($post)) return $settings;
    $shortcode = '[gallery ';
    $ids = get_post_meta($post->ID, 'pp_gallery_slider', TRUE);
    $ids = explode(",", $ids);

    if (is_array($ids))
        $shortcode .= 'ids = "' . implode(',',$ids) . '"]';
    else
        $shortcode .= "id = \"{$post->ID}\"]";
    $settings['neviagallery'] = array('shortcode' => $shortcode);
    return $settings;

}
add_filter( 'media_view_settings','media_view_settings', 10, 2 );


function ot_type_attachments_ajax_update() {
    if ( !empty( $_POST['ids'] ) )  {
            $args = array(
                   'post_type' => 'attachment',
                    'post_status' => 'inherit',
                    'post__in' => $_POST['ids'],
                    'post_mime_type' => 'image',
                    'posts_per_page' => '-1',
                    'orderby' => 'post__in'
                );
            $return = '';
                /* query posts array */
    $query = new WP_Query( $args  );
    $post_type = isset( $field_post_type ) ? explode( ',', $field_post_type ) : array( 'post' );
    /* has posts */
    if ( $query->have_posts() ) {
        while ( $query->have_posts() ) {
            $query->the_post();
            $return .= '<li>';
            $thumbnail = wp_get_attachment_image_src( $query->post->ID, 'thumbnail');
            $return .=  '<img  src="' . $thumbnail[0] . '" width="60" height="60" />';
            $return .=  '</li>';

        }

    } else {
        $return .=  '<p>' . __( 'No Posts Found', 'option-tree' ) . '</p>';
    }
            echo $return;
            exit();
    }
}

add_action( 'wp_ajax_attachments_update', 'ot_type_attachments_ajax_update' );

?>

meta-boxes.php

<?php
$gallerymb = array(
    'id'        => 'incr_metabox_featue',
    'title'     => 'Post options',
    'desc'      => 'Select post display options.',
    'pages'     => array( 'post' ),
    'context'   => 'normal',
    'priority'  => 'high',
    'fields'    => array(
      array(
          'label' => 'Gallery slider (use when Post Type is set to Gallery)',
          'id' => 'pp_gallery_slider',
          'type' => 'puregallery',
          'desc' => 'Click Create Slider to create your gallery for slider.',
          'post_type' => 'post',
        ),
      )
    );

ot_register_meta_box( $gallerymb );

?>

script.js

(function($){

    $(document).ready(function(){

        $('a.delete-gallery').click(function(e){
            e.preventDefault();
            $("#pp_gallery_slider").val('');
            $('#option-tree-gallery-list').html(' ')
        })

    wp.media.neviagallery = {

        frame: function() {
            if ( this._frame )
                return this._frame;
            var selection = this.select();
            this._frame = wp.media({
                id:         'my-frame',
                frame:      'post',
                state:      'gallery-edit',
                title:      wp.media.view.l10n.editGalleryTitle,
                editing:    true,
                multiple:   true,
                selection:  selection
            });

            this._frame.on( 'update',
               function() {
                var controller = wp.media.neviagallery._frame.states.get('gallery-edit');
                var library = controller.get('library');
                            // Need to get all the attachment ids for gallery
                            var ids = library.pluck('id');
                            $('#pp_gallery_slider').val(ids);
                            //update gallery list

                            $('#option-tree-gallery-list').slideUp();
                            $.ajax({
                                type: 'POST',
                                url: ajaxurl,
                                dataType:'html',
                                data: {
                                    action: 'attachments_update',
                                    ids: ids

                                },
                                success:function(res) {
                                    $('#option-tree-gallery-list').html(res).slideDown();
                                    $('#option-tree-gallery-list').next('p').hide();
                                }
                            });
                        });
            return this._frame;


        },
        // Gets initial gallery-edit images. Function modified from wp.media.gallery.edit
        // in wp-includes/js/media-editor.js.source.html
        select: function() {
            var shortcode = wp.shortcode.next( 'gallery', wp.media.view.settings.neviagallery.shortcode ),
            defaultPostId = wp.media.gallery.defaults.id,
            attachments, selection;

            // Bail if we didn't match the shortcode or all of the content.
            if ( ! shortcode )
                return;

            // Ignore the rest of the match object.
            shortcode = shortcode.shortcode;

            if ( _.isUndefined( shortcode.get('id') ) && ! _.isUndefined( defaultPostId ) )
                shortcode.set( 'id', defaultPostId );

            attachments = wp.media.gallery.attachments( shortcode );
            selection = new wp.media.model.Selection( attachments.models, {
                props:    attachments.props.toJSON(),
                multiple: true
            });

            selection.gallery = attachments.gallery;

            // Fetch the query's attachments, and then break ties from the
            // query to allow for sorting.
            selection.more().done( function() {
                // Break ties with the query.
                selection.props.set({ query: false });
                selection.unmirror();
                selection.props.unset('orderby');
            });

            return selection;
        },

        init: function() {
            $('.addgallery').live('click', function( event ){
                event.preventDefault();
                wp.media.neviagallery.frame().open();
            });
        }
    };

    wp.media.neviagallery.init();


    });
})(this.jQuery);

style.css

#option-tree-gallery-list li {
    float:left;
    background: none repeat scroll 0 0 #FFFFFF;
    border: 1px solid #CCCCCC;
    border-radius: 3px 3px 3px 3px;

    padding: 5px;
    margin:5px
}
#option-tree-gallery-list li img {
    display: block
}


#option-tree-attachments-list { overflow: auto; max-height: 350px}

#post .format-setting-inner p{
  width: auto !important;
    padding-right: 15px;
}

Hey I'm not clear on what the shortcode does. Could you explain that code above?