The official bezels Batocera uses for its decoration sets. These are bundled with every install of Batocera and can be selected by the user from MAIN MENU -> GAME SETTINGS -> DECORATION SET.
Each folder contains the "fallback" bezel in its root directory, and a bezel for each system in its system subfolder.
The exception to this is the default set "default_unglazed". This (hopefully) contains a unique bezel for each system, so no fallback is required. Please try to be conservative about how flashy it is!
In an installation of Batocera that is currently booted into, these files can be found at /usr/share/batocera/datainit/decorations/. You can edit these files to preview your changes.