If I could make a selfish VTT request? When you do VTT maps they should look "lit up" through out. This makes them look more realistic when light is actually used in the VTT. Since MapTool is my VTT of choice I'll use it as an example. I can drop all the tiles into MapTool (MT) and then cover the whole thing with "darkness" and with "fog of war". Then for the character tokens I give them their own light source such as a torch, spell, or even dark vision. Now as they move around on the map it exposes what is below the fog of war and also lights up the area they move into. So by having a map that is already "lit up" it will look more natural. If it is already dark and gloomy, when it gets "lit up" by their light source the PCs will ask "what sort of magical darkness is this?". If you get what I'm saying.