For Retina iMac, Vivaldi Wallpaper
In recognition of the fact that most people probably don't want a screamingly bright red screen, here's a grey one:
If anyone wants a really dark based one, let me know. More than happy to make it.
But wait, I know you want more:
Saw your other one you posted earlier in All Platforms. These are really nice, too.
Here are a few of the official ones: