im_sc_extender.php

<?php

register_plugin(
    basename(__FILE__, '.php'),
    'SimpleCatalog Extender',
    '0.1',
    'Your name',
    'your website url',
    'A SimpleCatalog extension',
    '',
    ''
);

add_action('imcatalog', 'action');

function action()
{

    class ExtendedController extends \ImCatalog\Controller
    {

        public function renderSection($sectionName, $params = array())
        {
            if($sectionName == 'FrontendItemDetails') {
                $this->renderFrontendItemDetails();
            } else {
                return parent::renderSection($sectionName, $params);
            }
        }

        /**
         * There is your extended method
         */
        private function renderFrontendItemDetails()
        {
            $currentItem = $this->processor->getItem($this->router->currentRoute['categoryid'], $this->router->currentRoute['id']);
            if($currentItem && $currentItem->active != 1) $currentItem = null;

            $itemDetailsContent = $this->getTemplate($currentItem);
            if(empty($currentItem)) {
                $this->content = $this->parser->render($itemDetailsContent, array(
                        'description' => Util::i18n_r('err_item_not_found')
                    )
                );
                return;
            }
            $output = $itemDetailsContent;

            foreach($currentItem as $key => $value)
            {
                if(is_array($value)) continue;
                $output = $this->parser->render($output, array($key => $value));
            }
            $this->content = $output;
        }

        private function getTemplate($currentItem) {
            ob_start(); ?>
            <div class="sc-element-wrapper">
                <?php
                $output = '';
                if(!empty($currentItem->image))
                {
                    $path_r = '';
                    $path = '';
                    foreach($currentItem->image as $key => $image)
                    {
                        if($this->processor->config->itemDetailsImageResize)
                        {
                            $path_r = \ImCatalog\Util::getResizedUrl($currentItem,
                                $key,
                                $this->processor->config->itemDetailsImageSizes[$key]['w'],
                                $this->processor->config->itemDetailsImageSizes[$key]['h'],
                                'resize'
                            );
                        }

                        $title = isset($currentItem->image_title[$key]) ? $currentItem->image_title[$key] : '';

                        $output .= '<figure>'.
                                  '    <img src="'.$path_r.'" alt="'.$title.'">'.
                                  '</figure>';
                    }
                }
                echo $output
                ?>
                <div class="sc-element-details">
                    [[description]]
                </div>
            </div>
            <?php return ob_get_clean();
        }
    }

    $catalog = new ExtendedController();
    \ImCatalog\Factory::buildCatalog($catalog);
}