I am lucky enough to have an art pen pal and I can’t tell you how much I love it. I highly recommend getting one! This idea for a wall of envelopes filled with good messages is a local type thing. Maybe it would work with art swap?
Pop on over to Hub Pages for a whole great post filled with Guerrilla Art like this envelope good wishes wall.
I think you mean “guerrilla” art. They are not interchangeable
Thanks for the correction!