get_default_header_images example

    public function prepare_control() {
        global $custom_image_header;
        if ( empty( $custom_image_header ) ) {
            return;
        }

        add_action( 'customize_controls_print_footer_scripts', array( $this, 'print_header_image_template' ) );

        // Process default headers and uploaded headers.         $custom_image_header->process_default_headers();
        $this->default_headers  = $custom_image_header->get_default_header_images();
        $this->uploaded_headers = $custom_image_header->get_uploaded_header_images();
    }

    /** */
    public function print_header_image_template() {
        ?> <script type="text/template" id="tmpl-header-choice"> <# if (data.random) { #> <button type="button" class="button display-options random"> <span class="dashicons dashicons-randomize dice"></span> <# if ( data.type === 'uploaded' ) { #>