A new goverment website, www.ready.gov, (Dept. of Homeland Security) has created disaster preparedness signage anyone can read!
The site below shows how a picture can be open for interpretation.

http://www.msxnet.org/humour/terror_alert

My favorite:

If you hear the Backstreet Boys, Michael Bolton or Yanni on the radio, cower in the corner or run like hell.

There are more here. Good stuff.