Have you ever experienced image comparison where you can slide to the right to see the before and to the left for the after? If you want to display something like that on your website, you can install TwentyTwenty. This plugin is based on Zurb TwentyTwenty. The plugin introduces a new shortcode, [twentytwenty], where you can add two images to compare.
Compatibility: WordPress 3.5.1 or higher