Chromecast has started showing Google Home voice tips to some users who are already posting about the results on reddit, as well as uploading screenshots of what the tips look like. Google already does an ok job of letting users know what kinds of things you can ask Google to do by voice, but these new tips showing up on the backdrops of Chromecast-connected TVs and monitors seem to be geared directly towards apps and services that you can use with Chromecast, meaning apps and services that can be streamed to the device.
CBS All access for example is the official streaming TV service for the CBS network and the app allows you to watch various shows on your phone that are both available on CBS through cable and available exclusively in the app. Instead of opening the app and tapping the Chromecast button on your smartphone display, if you have a Google Home, Google Home Mini, or Google Home Max you can simply ask Google to stream your shows. To do this you'll need to connect your CBS account to the device through the Google Home app, as is probably expected.
According to the poster on reddit you don't need to necessarily have accounts with or use the services of the apps which are being promoted on the screen, as the user noted that they didn't have accounts with either CBS All Access or Viki. It's not clear how many different services users will see on these new backdrop Google Home tips but it's likely that Google will end up promoting more than a few of the bigger services that work with both Chromecast and Google Home. The tips appear to be a test that Google is running on certain Chromecast devices as it doesn't seem to be available for all users and the tips look to be popping up at random. If this is just a test for the time being then Google may not end up rolling it out fully at all if the reception isn't positive enough from users, though it's just as possible that Google could push things out on a wider scale as time goes on.