Chromecast will now let you go through those pictures that were shown on your screen so you can learn a bit more about them. Also, the app had a few layout changes to focus on the backdrop history feature. There is a card for your current active Chromecast(s) with a button below the image preview , tapping that will led you to the most 5 recent images with the respective links to their official source.
Quoting from Chromecast app on Google Play :
Redesigned devices view, showing devices as cards with backdrop and casting status
Added setting to change backdrop speed
Browse through history of backdrop images recently shown on your Chromecasts
Improved reliability and performance of backdrop cards
Improved multi-user and multi-Chromecast backdrop settings
You can wait it for the up date via the playstore or you can install it manually via the APK file available on APK Mirror.