The official bezels REG-Linux 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 REG-Linux that is currently booted into, these files can be found at /usr/share/reglinux/datainit/decorations/. You can edit these files to preview your changes.