Take this with the proverbial grain of salt, given the pre-release nature of the software being examined, but the folks at XDA Developers have discovered what appear to be extra customization options hidden in the leaked Android Q build they've been tearing through. Although the settings aren't user-facing, a few new so-called "overlay" packages were found in the image which allow for changing between a handful of pre-installed fonts, icon shapes, and accent colors.
Left: Rounded rectangle icons. Center: Rubik font. Right: Purple accent. Images all via XDA Developers.
In all, XDA found two pre-installed fonts, four icon shapes, and three accent colors in the Android Q images it examined. Further, Android Q itself has started categorizing overlays into those three groups, which should make managing logic for theming a bit easier. However, there isn't any configurable, user-facing option setting for switching between them, these new options had to be individually enabled via ADB.
For some perspective, previously Pixels only had three overlay packages: a notch/display cutout accessible via Developer Options, the Pixel framework, and a partial dark theme.
It's possible these new additions could land later with a user-configurable settings pane, but it's also possible they'll be stripped out at some point. They could merely represent a test for more tightly-integrated OEM customization. Google hasn't been in favor of custom themes recently, it would be a bit surprising for them to change stance on the subject so soon.
- XDA Developers