The official bezels RetroBat uses for its decoration sets, forked from Batocera's decorations sets.
These are bundled with every install of RetroBat 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!