I was thinking about guerilla gardening and similar things and wondered if we could maybe come up with similar ideas to brighten the areas around us. Guerrilla gardening, if you don't know, is basically where you plant flowers on, say, a disused patch of dirt next to the road. Or planting herbs for people to pick and use at their own discretion!

I wonder if we can't come up with similar things. The only thing I can come up with is along the lines of inspirational graffiti, but obviously that isn't legal in most places.

Any ideas?