I'm normally extremely anti-graffiti, but some of these are excellent! 

I liked that a bunch. Thanks!

Hi,
 
That music needs some serious psychedelics!
 
Put me to sleep!

Liked it!
 
I can't really say that a good 95% of those are actual vandalism, but rather acts of artistic creativity and humor. I would't mind seeing some of that in real life around the neighborhood. It has me thinking to keep my eyes open for some ideas when I walk the dogs.
 
And how many of us would be tempted to embellish if we ever saw a sign indicating "Stairway 2"? 

The most common stop sign graffiti I saw during high school was adding "Disco!" underneath.