The biggest problem I see with this is potential for vandalism, and then making sure the graffiti fits in with the aesthetics of the game. But mostly vandalism.
+1 Sounds good...too late about the vandalism part, people can write obscenities on their notes or in animal names. The community should be able to flag it as inappropriate.
I named my chicken Bum. It seemed appropriate since I'm squeezing him.
That would be pretty cool. It could be the second level of Penmanship or something. Ix has a few walls too and i've always wanted an industrialized area.
I notice you keep using the term "vandalism". Glitch has no capacity for vandalism considering the game's code defines what you can and cannot do.
Currently you can leave a note on a street. It could be dumb/engaging/informational/rude/amazing but they all look the same. I would like to leave something on a street that is a lot more visually interesting. Perhaps something that anyone else can pick up and take if they wish. Or maybe something that lasts for a game day, or a portion of a game day, but can't be removed. I personally would assume that if something like this were possible, the art would be in line with the overall theme of the game. Which would make it not vandalism.
...All right, maybe "vandalism" isn't the right term, and we can play semantics. But surely we can all agree a horde of chickens all named "Hitler's Bloody Vagina" isn't the most aesthetically pleasing, and perhaps the act of a downright unpleasant person. And when I think "graffiti", I think writing and images on property, usually big enough to be seen from a distance. At least you can only see chicken names if you're close enough. But giant, in-your-face, "HITLER'S BLOODY VAGINA" (in admittedly pleasing typeface) would be worse, right?
If graffiti / street art / tagging / whatever other term I may or may not be using correctly is implemented, there has to be a way so that environments aren't inundated with a hundred or so pieces all trying to get a message out there. I'd also want it to be a high-tier skill, like naming animals is with Animal Kinship V.