The light template could serve as a second fog overlay. The player can’t see anything outside of his or other token’s light zone. As an option, you could obscure tokens in shadow showing only the position and size but not the image. This way the player knows something is out there and the approximate size but not what is actually there.
This has more uses than just dungeoning. A DM could use the light overlay to simulate dusk/dawn conditions outside to represent how far a player can see even without torches. This also works for weather conditions like fog, sandstorms, rain, etc. For city adventures you could place tokens representing street lights with their own light overlay so the players see a shadowy alley but don’t know what’s in it until the get close.
You can abstract this for sensors on vehicles as well. In a starship game, the light function can work as active sensors with the shadow representing information gained from passive sensors. In this case you would know a planet it out there and its size but know nothing about its composition until you pulled within active sensor range. For submarine games it could represent active vs. passive sonar sweeps. For fighter jet games you might see a radar signal coming in but not know what is producing it until you had line of sight.
Another application of the light overlay is to show how far you can move in a round before you move the token. Yet another application is to show the range of a ranged weapon with the shadow representing the second range increment.
I suppose that's enough for now. How’s that for a Friday ramble.
