Whenever I'm designing the maps and layouts for my campaigns, I have to draw on the map layer (usually because if I have something on the token layer it'll get deleted or moved away from position) and I find that having multiple map layers would be extremely useful. Maybe have the ability to add new ones? I find that whenever I have to delete something off of the main map layer, I end up deleting the actual map frequently, and not the small mark that I meant to get rid of.