I don't know how hard it would to achieve, maybe notes/reminders that you write throughout the day?
A layer indicator?
An animation going faster and faster when you type?
Your keyboard 3d model slowly rotating?
Time in different timezones?
Random words of encouragement to keep you up during the day?
State of ctrl/alt/super/shift/caps lock/num lock?
Hmm… WinAMP-style visualizer with an intensity based off of your WPM? Or maybe a character face that looks drowsy when idle, but reacts when you start typing? A breakout or Tetris game that plays itself? Snarky quotes making vague observations about your current typing tasks? (“Wow, look at all those numbers, someone must be a math wizard.”)