Yep, create a character called "Campfire" or "Light Source" or whatever you want. You could create a rollable token with all the different images of light sources you'd use in you want. Then take the token and set up the lighting the way you want, set it to represent the "Light Source" character, and then go into the "Light Source" character and save that token as the default token. Droppable Torch Token Invisible Light Token