Inside the latest beta for Google Messages, improved customization options for your individual chat threads appears to be ready for mass rollout.
Google has been working on these features for a bit now, as code surfaced back in April which detailed what we could expect. Now we have actual screenshots of the app with the features, such as custom colors for threads, as well as full wallpapers with selectable options.

To access this, you’ll head into a chat thread, tap the three-dot settings button, then select Chat Themes. Beyond the predetermined chat theme color options, you’ll see a “Choose a photo” option which will bring up wallpapers.
This feature looks very close to completion, so if you’re in the beta for Google Messages, be on the lookout for it to hit your Android phone.
Google Play Link: Google Messages



