Recovering from my last note, this is an opposite post, and hopefully a little more positive one. A simple, black wallpaper that shows some of the more common (and some less common) commands and what they do.
It might be an interesting twist to a dark-themed setup, or even better, as the backdrop for a transparent tiled desktop. Hmm. 
The only downsides, as I can see, is that stretching or squishing it to any other dimension than 1280×1024 is going to make the text somewhat difficult to read. There are ways around that though.
Courtesy of korben.info, and Tux-Planet.fr, as an intermediary.
Küwl – I like it
I use the whole (tiling, Ion3) screen real estate fully though so I guess I wont be borrowing this nor any other wallpaper..
@robusku
You could use transparency in your terminals
As suggested in the article
I just recently moved to Linux and one of the first things I did was applying this very same wallpaper so I would learn to use the cli. By the way, I use 1280X768 resolution without problems.