A really small act is able to cheer you up and increase your productivity: changing your desktop wallpaper at least once a month. And that's simply because no one likes to fall into a daily routine (even with such a small thing), and if you keep the same wallpaper for too long, you'll get bored really easily.
With that in mind, I've selected some beautiful black wallpapers from some of my favorite websites. Some are photographs, some are illustrations... but all of them will most definitely increase your satisfaction during work hours. So here's my selection, I hope you enjoy these. Cheers! ;)