Graffiti is really cool but it doesn't leave a special mark saying "This is me who put it",
For X-Crystals you should be able to buy a graffiti with your name on it, it will be the same graffiti background for all players but the text on it would change depending on your username,
It's text size should fit the sizes of usernames,
This should be only for X-Crystals, so that it gets even more rewarding to donate to the game and it's just pure cosmetic feature.
( Forum: http://en.forum.tankix.com/topic/1603-username-graffiti/ )
Customer support service by UserEcho