I think you can uncomment the line here that begins with Option in your file ->
# Set the basic blanking screen saver timeout.
Option "blank time" "10" # 10 minutes
I think that will cause your screen to blank even if you're just running a terminal, but I'm not totally sure. As far as I know, you can't run an actual screen saver from command line because you'd have to have a X server for the screen savers to display.