Improvements to the random pictures announcing on kill

Added a new picture, you will like this one.
Changed that one .jpg URL that actually pointed to a .gif file to .jpg.
Changed picking algorithm to have fixed chances even when adding new pictures. Uses random.choice().
We don't want to have these pictures quite as often. We once had a 1/100 chance. To balance things out a bit, a 1/50 chance should do.