I can see what you see. This is standard image size. If you want to set it smaller, you can edit it in admin -> system -> settings -> appearance. for Product List Width and Product List Height.
This will change the size of all images in listing pages and other places.
If you need to change this only in specials file, you can set it to Product Image Thumb Width and Height.
To fix you can edit this file: storefront/controller/blocks/special.php
change:
$thumbnail = $resource->getMainThumb('products',
$result['product_id'],
$this->config->get('config_image_product_width'),
$this->config->get('config_image_product_height'),true);
to
$thumbnail = $resource->getMainThumb('products',
$result['product_id'],
$this->config->get('config_image_thumb_width'),
$this->config->get('config_image_thumb_height'),true);