In the latest Antiquity Game Play Video they showed a 'Trade Route' which looked pretty bare - a line with, I believe, some arrows in it.
Frankly, it looked to me like a Place Holder that may be replaced by a better graphic before Release, hopefully with caravans/trade ships moving on it. I seriously hope that they don't allow 'pillaging' to completely destroy a Trade Route, because that is simply Fantasy. If a route got raided, it got moved to another route, either water or land, not shut down unless there was simply no way to make a profit on it any more.