We geeked out earlier this week and sang the praises of the command line. If you'd like to keep up on your commands, this wallpaper floats some of the best over a simple black background, with a touch of style.
These are Unix-style commands, so they work natively in the Mac's Terminal and in Linux — Windows users would need to install Cygwin to make use of most of them. They're written in both code and plain English, and there's plenty of space for desktop icons on the left if you need them.
I wasn't able to track down the original source of this wallpaper, but it has made its way to a few different Linux and geek-friendly forums. If you do know the original source, post it in the comments and we'll update the post for proper credit. In the meantime, share any other wallpaper that provides command-line knowledge in the comments too.
Handy wallpaper for basic linux commands [Tux Training]