You’re right that adding anything that helps us to get light effects (e.g. a game map in the dark with some light torches or etc) would be helpful and very welcome.
As for adding one light, there’s only a way to make one non-shadowed “light” that I can think of by using alpha opacity. That is, to have a black image (can be layer, can be higher zdepth), which has an alpha opacity hole inside of it. That way, “light” can pass through the circle perfectly, while all of the outside light is filtered out by the black image.
Something like this:
Image in gimp with layer mask, where on the layer mask part, a radial gradient is applied.
I would ideally make the entire image have about 90% to 99% opacity so that a little bit of light can pass through the black parts too.
By stretching the circle, we could make a sort of “headlight” effect.
We could also add a 15% yellow tint (15% visible background layer in Gimp):
But using this method to make 2 lights would be difficult (Edit: or moving lights, while possible, you need a lot of black background size).