CSS3 Lightbox (Click on the images for testing purposes of this lightbox plugin.)
This lightbox plugin is in active development and will be updated on a regular basis - Please do not rate negative before i tried my best to solve your issue. Thanks buddy!
The plugin parses all your images in your blog posts and creates some specific classes for this images which are called from a smart and complex css file. This css entries are able to open your images in a very nice looking lightbox.
Install it via the admin dashboard and to 'Plugins', click 'Add New' and search the plugins for 'Lightbox CSS2'. Install the plugin with 'Install Now'.