Create an automatic screenshot generation feature. It would work like this:

When enabled (via a setting that enables a "generate screenshot" button) Optimizely will load each variation - behind the scenes - including the control and create a screenshot based on the target audience. (i.e.: laptop, desktop, tablet, mobile - using average sizes or customer's defined UX design).

The images can be updated manually if needed.

This will save tons of time doing this manually.