Here is a simple but handy Open Content customized template for display before/after images with a slider. These are good for renovation pictures, health and fitness, etc.
You can download the zip file and read use/install instructions from my github repo
Once you have an instance of Open Content on your site, simply go to the "Template Exchange" link as show below and import the zip file.
It includes the option to switch the orientation for the slider from horizontal to vertical.