According to Mashable, perhaps the most noticeable feature, especially for people who like to tinker with their phone's visuals, will be the themed app icons. Until now, only Google's own apps would get the dynamic colouring depending on the wallpaper/theme you used.
However, in Android 13, this will extend to all icons. To make this work, developers will have to tweak their icons a little, so don't expect every single icon to be "themeable" right from the get go.
Google has said that themed app icons are initially coming to Pixel devices, and will roll out to devices from other manufacturers later.
Another cool new feature is a new API that will let developers set a separate language in their apps. This will be useful for multilingual users, who will be able to set one language as their main phone language, and specify a different language in certain apps.
On the privacy front, Google now has a new system photo picker that allows for more granular privacy controls. It looks similar to the photo picker for sharing photos with someone. Users will be able to select photos and videos on their phone which will give an app access to those photos and videos alone.
As per Mashable, for Android 13, Google has said it plans to reach its Platform Stability milestone in June 2022, which should give developers "several weeks" to perform testing before the final release is out.