Awesome, this time I want to be in too!
It would also be fun to have two themes, one for each side. Like Team Fortress 2 has, but of course with different themes than Team Fortress 2.
It wouldn't even be necessary for the 2 themes to match up in style. We could go for a "Who framed Roger rabbit" kind of world with a cartoon-ish (Jouste) style at one side and have a Victorian London style at the other side. Of course the middle would be a mix-up of the 2 themes.
This would require an art director to make sure everything fits together.
I realize while writing this that it might be a bit to complicated for a "small" and "simple" project. But I figured I might as well throw it out there, maybe it'll get you guys to think of something awesome