One of my team members built an entire QA tool around this idea. It can load thousands of URLs, run it once, and then after a deploy to the development servers it runs again to generate a visual diff report. A combination of Golang, Node.js(PhantomJS), and some other bits I forget at the moment.

The product managers and content teams love it since they can quickly skim through a report to find visual bugs that may have gone unnoticed otherwise.