This simulates an eye blink every 6~10 seconds.

Create the following functions in your script file:

void Blink()
{
          FadeOut(0);
          FadeIn(0.1);
}

void BlinkTimed( string &in asTimer )
{
          Blink();
          AddTimer ( "", RandFloat(6,10), "BlinkTimed" );
}

Then, add this line to your OnStart()

           AddTimer ( "", RandFloat(6,10), "BlinkTimed" );

With this code, the screen will simulate a blink every 6~10 seconds.

Amn.-