I've been running a game using LMoP version 1.3, and noticed that several maps have the background image set to emit light. I just created a fresh game using the LMoP module to confirm, and it looks like basically all the maps are set to emit light of 60/30 and have the "Has Sight" box checked. I took screenshots of the initial settings on Cragmaw Castle, and then a box drawn on the dynamic lighting layer around the center of the map (as that's how I figured out where the light was coming from).