The magic about black wallpapers is that you can see your reflection on your screen! (Provided you have a glossy screen :) And you can give a glance at your looks time-to-time :P I'm sure you have tried this and if not you should try it now!
I always keep blackish wallpapers but I also keep in mind that *Work is IMP* :)
Click on the image to download.
Try the white one too... But the black is more dynamic!!