I made a slang shader that mimics some of the effects/borders available on the SNES Mini (in your video settings, aspect ratio needs to be 16:9, integer scale OFF): https://www.mediafire.com/file/yggrh9iiu4437ij/mini-border-shader.zip You can cycle through the borders using the ‘Background’ runtime parameter. The first 2 use the average color of the screen to make the glow effect match the game. You can also toggle scanlines (on by default; I used a non-integer scale-friendly scanline algo) and do some other image/aspect tweaking, if necessary.
Here’s what it looks like at 1080p non-integer with the default, ambient-glow border:
and here it is with the ‘speakers’ border (bsnes core, crop overscan OFF, TOP/BOTTOM overscan masking to 0.03 each): I’m not planning to add this one to the official shader repo, since those are Nintendo’s border images, but I thought I’d share it anyway in case someone enjoys it.