We're fortunate to have a place to celebrate the wedding where we can have slow growing decoration. We will have some summer flowers like sunflowers, marigold and Indian cress among others in borders by the barn, but if you're in a woodland environment moss graffiti might be really cool, and it fits better in that environment than sun loving annuals.
The recipe I was taught when I was becoming a gardener was moss, some soured milk/yoghurt and some water. Whisk the moss and yoghurt well and add water until you get a paint like mixture and use an ordinary paintbrush to paint the surface you want to have moss on. If it's dry you might need to spray it with water. Quite soon you'll see the result of your work.
There's also a beer recipe where you whisk moss with beer, buttermilk and sugar and paint it the same way as with the recipe above. Some recipes say you should use a mixer, but I personally care too much about my mixer to do that.
More pages on the subject:
Stories from space
Inhabitat
Apartment Therapy
Craftzine
There are many other sites out there writing about this. Spreading moss by painting it on objects isn't exactly new knowledge and gardeners have known about this for very long, though it wasn't called graffiti (I dare to say centuries here) but it can never be repeated enough. Go forth and spread the knowledge!
