Blacklist site notice banner images

Images inside the current WLA banner are getting picked up, spamming
all Media Viewer users with large-scale couscous imagery.
Couscous is nice, but too much couscous will make you bloated.

Change-Id: Ie5726be6de97da13e8dc650031285f899c2d6440
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/1011
Merge "Blacklist site notice banner images"