1. Don't be afraid of "white" space (yellow in this case)
2. I think this is a great color scheme... someone mentioned the other day that there aren't many non-blue, cool-color machines. This is a pretty good example of one that isn't blue.
3. I think you COULD add characters, but I don't really see why it's necessary.
4. The controller is fine. Your cab is simple & not over the top. Again, don't be afraid of simplicity. I don't think it wins awards for a WOW factor, but it looks good. If I were you however, I would remove most of the admin buttons. I have mentioned before the uneccesary nature of admin buttons if your ipac setup is done right. Adding extra buttons arbitrarily for admin functions is more confusing rather than less, it's not attractive, and it's lazy... I have many reasons I can site, but only if someone is really interested.
All in all, good job. Where are you going to have the art done?