Google Classroom has given the teachers to the ability to change headers for quite some time. So nothing new there. Most people use them by giving each class a different header to help differentiate between them. Its a gGood idea. And it works. One way that you may not have thought of using the header to generate interest in a new unit. You might even use it to draw attention to an announcement or have a reminder on it. One way I like to use them combines to ideas. It allows for class differentiation as well as prompt interest in the new unit.
The process would be the same that you would go through in creating a custom header. As you create the new header you could use images that connect to your new unit's content. Occasion, I find great photos that students like. They not only generate not only interest, but they also spark questions. I love it when a student comes to me the next day and shares with me a ton of information they gleaned from research that I never assigned!
The second part of the equation is to tint your header so that it helps create the changes needed to keep your classes straight. Turn up the purple for one, give another a green tint, and adjust another to a nice blue hue. Many online photo editing sites will have simple ways to so this. It may all happen in the cloud, but it won't rain on your parade.
This simple hack will allow you have the best of both worlds. You get the hype to help pique interest and keep your sanity as you can tell which class is which. So simple, but so helpful. If you try it please share with me your version. I would love to see them.