>>2243046The one you posted was simply stretched to match that dimension. So, I upscaled the one from danbooru, added some grain and tweaked the saturation, then stretched it.
I also have a 'clean' upscale without stretching here, if some anon would like to try content aware fill or some sort of frame to make it 16:9.
https://files.catbox.moe/ykqdrv.png