Bezel art and overlay layout from libretro's common-overlays (gamepads/gb_anim_portrait), licensed CC-BY-4.0: https://github.com/libretro/common-overlays

overlay.cfg is the upstream gb_big.cfg, unmodified. It ships as the reference skin for the RetroArch-overlay loader in src/core/TouchSkin.lua: a full-device bezel, per-button press art, a screen viewport, and page switching between the DMG and Color shells.