THIS IS THE END
This is what I did in BASEMENT43 myself in December 2009. Its an array of incandescent lightbulbs controlled by a series of timing wheels and mechanical switches and the bulbs spell out, one after the other, the words: THIS. IS. THE. END. Which indeed it was - of BASEMENT43, that is - because Islington Council took the building back in the New Year.
The words were hard to read and effectively un-photographable.