Besides the needed improvement of your ESD-protection circuit, as mentioned in an earlier post, You should think about a way of harmelessly shunting the ESD-energy arround your mainboard!

Think about the person running on the belt. If he wears shoes with a rubber sole, then at the moment he begins to run on the belt a charge separating process is invoked making the person's body to become charged and charged and charged... Touching any metallic stuff that is connected to the rollers will offer the collected charge a discharging path to the rollers then, resulting in a heavy and painful ESD (electro static discharge). Using isolated material only will not solve the problem, because when he touches the keyboard, where there's a break in the isolating barrier, the charge will find a discharging path. Also, the charge on the person's body will become higher and higher and higher if everything is isolated.

So, for all the touchable surfaces you should provide a coating which is able to let the collected charge to flow, but at the same time limiting the discharging current to a sane level. This will avoid painful discharges and limit the collected charge on the person's body to such a low level, that a standard ESD-protection scheme will prevent the mainboard from running ill.

Kai