Here is a beginning of a collection of overlays that I made first for myself, but that I share here. They concern Aracde emulators (Mame*, FBaplha). The goal here is not to stick to the realism of the original Bezels but simply to make the screen less empty. For vertical games there are two formats (16/9 and 4/3), all for a “Core Provided” ratio aspect.
All files are to be put in the overlays directory (~/.config/retroarch/overlay).
The files are in this GIT repository: https://framagit.org/wiltur/retroarch-overlay