Can't you just make a rectangular image of the right size in an image editor and fill it with black? Or take a photo with your camera's lens cap on (set to a short exposure on manual/shutter priority if possible) then set that as the background? Or make a black Keynote slide, export it as a JPEG then change the size in Preview, then use that?
Where can I acquire a jet black wallpaper for my space gray plus?
Do you have the same pictures for the 6?
Thanks. I discovered how to put invisible black icons so that they can be positioned to push live icons lower and within reach on a 6 plus.