This reminds me of Sweden's best April fools joke in 1962 : http://www.museumofhoaxes.com/hoax/Hoax … _Color_TV/
My own favourite is similar to yours: I take a screenshot of my roommate/colleagues screen (using the printscreen key) and paste that screenshot into a new photoshop or windows paint document (using ctrl + V) then I draw lots of dirt on it (using the computer program not real dirt!) and set it as the screensaver. activate the screensaver and unpulg the mouse and it will look like its crashed!