I think it'd be quite cool if each clan could choose a "clan colour", so that, during battles, each player of the clan uses that colour (lighter/darker to differentiate between team members). The most obvious problem is that two clans might pick similar colours, in which case, should they fight one another, I suppose one could default to the default blue/red...
Just something I thought of a couple of days ago, thought I might as well mention it :-)