Place it in your RetroArch/thumbnails or a dedicated backgrounds folder.
While RetroArch includes built-in color presets, third-party creators host advanced themes on platforms like GitHub and Reddit. retroarch custom themes download
: The primary hub for new theme releases, feedback, and user-shared creations like "Midnight Blue Ozone" or "NeoActive". Place it in your RetroArch/thumbnails or a dedicated
Search for: "RetroArch custom theme pack download" find assets/xmb/ .
Inside your RetroArch folder, find assets/xmb/ .