My opinion on "Go Bombing Day" is the same as how I feel about "Go Skateboarding Day." Rather than devoting a certain day out of the year to doing it, just be out there as much as you can doing it. Granted I'm not really "out there," but I still feel it's best just to do what you can, whenever you can.
On the other hand, I think it would be chill just to get as many people together for a day just to skate and/or paint. I'm all for getting big groups together just to chill and have everyone do their thing.