Think Joes point is pretty spot on (his first one, although I laughed out loud at that lawnmower pic!). If you do get a sticker like that out, then it'll just create a community of people who have thos stickers on their cars.
Plus there was only one design I even remotely liked and it got thrashed!!
In general I wave to any other dubber I see if they look like theyre in 'the scene', although I often see people wave at me just after I've driven past them, so everyone probably thinks I'm a miserable b@stard!!!
I generally get waves off of aircooled and watercooled alike. I'm pretty much the solo watercooled member of a local aircooled club, but theyre all cool with that! Also when I dorve a scirocco I did find them to be a bit clicky, got waves off of every scirocco I passed! Found anyone in a dub seemed to wave at the scirocco.
Have never had as many waves as when I drove the Beetle tho!