Well I can think of one message we could probably all identify with, despite differing personalities and locations and so on.. Personally I think street art is best used as a form of activism rather than just doing it for the sake of doing it. Everyone who appreciates it on an artistic level is sick of those shitty tags that kids scrawl everywhere, and those artists that make large scale works or just work hard to make something good would benefit from the removal of the threat of being arrested or fined. So basically my theme idea is Make Street Art Legal. I think it would more or less eliminate the low-grade, two second shit from the public domain, since there would be no kick from doing it anymore just because it's illegal, and as I said, the good stuff would just get better and more plentiful. The number of artists using street mediums would increase a thousandfold to include all those who don't want to break the law or don't have the balls, or just don't have the time for night missions. I think Bansky wrote an awesome snippet that would complete the selling of my idea - Found it;
"Imagine a city where graffiti wasn't illegal, a city where everybody draw whatever they liked. Where every street was awash with a million colours and little phrases. Where standing at a bus stop was never boring. A city that felt like a party where everyone was invited, not just the estate agents and barons of big business. Imagine a city like that and stop leaning against the wall - it's wet. "
Shit load of the graffiti in LA is nothing but idiot kids/gangs and their scrawls on building and walls. All the awesome stuff is hidden under freeways or in little corners of anywhere really where you wouldn't think to look. I hate the random signatures of dumb kids giving this kind of art a bad name.