It looks like paulb-nl has just added the ability to load custom Super Game Boy borders, when using MiSTer’s Game Boy core. This feature is now merged with the main project and running your favorite update script should automatically install it; I’ve been using ‘update_all’ these days. After updating, create a “SGB Borders” folder in your Games\GameBoy directory and copy the border files there. I included a link to borders shared with me, but there might be a more complete set available.
update_all script: https://github.com/theypsilon/Update_All_MiSTer
SGB Borders: https://www.retrorgb.com/assets/SGB_Borders_2021-03-29.zip
More MiSTer Info: https://www.retrorgb.com/mister.html
Main Post: https://www.patreon.com/posts/gameboy-49349355
Previously, toggling the SGB border option would pull the custom border from the ROM file, for games like Donkey Kong or Link’s Awakening DX, but enabling it on a non SGB game would show a black border. This new option allows you to choose whichever border you’d like.
…and as always, thanks so much to the entire MiSTer team for bringing us these awesome enhancements!