Unlike games such as Minecraft, where you can increase the render distance to a ridiculous distance as long as your PC can handle it, the W3D engine is set up a little differently. As Pushwall said, it won't really have an effect without changing the fog level of the map itself, which as he mentioned, is there by design. Rendering objects beyond what the fog will allow you to see would only slow your system down, and still not allow you to increase your view distance, which is what I believe you are actually looking for.
And most likely, the render distance is already farther than what you can see, as it is a global setting (not per-map). Notice on large clear maps like Ridge War, you can see a long way! Therefore, increasing the render distance would do absolutely no good.