I have seen interesting videos and protests of people using light to project protest messages on buildings.  These guys started me thinking about this, and it seemed intriguing, so I set about to see a simple way to try this. The easiest thing I found is the EZ Gobo, which is a battery powered single unit.  It's light, pretty cheap, and easy to use.  The battery can last up to five hours.  However, it's only 10 watts, so it doesn't throw a lot of light.  This is actually an advantage, though, because it doesn't throw enough heat to harm non-metal gobos.  But this is just an experiment anyway, so there's that.

You can make your own customized gobos, which are the black 26mm circular discs that block the light except for the design you designed into the gobo.  They can be made with transparency sheets and a printer for really cheap, or you can buy a professionally made metal one for about $40 or more (this one is metal).  Changing gobos is also easy.

This first photo is from a closed Publix store, so there wasn't much light around.  I think it looks pretty good.