I played around a bit with this myself and ran into various problems.
Making the default fog of war a bit transparent reveals a few problems under the hood:
1) There's still some grid paper graphic drawn undernetah (hidden by the fully opaque black), this is an easy fix in next beta version.
2) The fog of war tiles are drawn to overlap each other a bit right now. This creates a structure that looks like a solid black grid. I wonder why I needed the overlaps in the first place - I think it was related to the the movement of light (flicker).
It will take me a bit to sort this, but - as always -we will get there