Nice work! We have a similar feature built into Ghost Inspector: https://ghostinspector.com/#visual-regressions -- It includes a tolerance setting so you can basically say "I only want to hear about it if the screenshot changes by xx% or more." Effective visual regression testing at scale is tough though and is really more of a secondary feature for us.

If anyone is interested in other solutions, ImageMagick has a nice "compare" tool built-in. There are also plenty of open source projects like Huxley, PhantomCSS, etc. I recently saw a demo of Applitools Eyes (https://applitools.com/) and it's quite powerful (though it's a paid service).

Lastly, I did a presentation that involved visual regression testing here: https://www.youtube.com/watch?v=mK0l__jmpTA (starts around 12:25)