Can I make images or videos full screen?

Yes. This can be done for individual screens in your ArcLab module.

At the Screen Settings panel on the right of your ArcLab Editor – toggle Make Media Full Screen to “Yes“.

Note
1. How to add media to your ArcLab module screen: https://arclab.io/knowledge-base/adding-media-to-your-module
2. If an image or video is made full-screen,  the button at the lower half of the screen would partially obscure the media