Currently I don't think there's a way to set up a light as a torchlight like you describe, but you can create an empty model which emits light and use it as a tile, an object or even a character, and script it to move or appear/disappear when needed. There's no function to globally control the lighting of a map yet, so you'll have to set up a level with dark lighting and colors and use local light sources for now, but I believe Justin has planned more lighting-related features for the future. The new Godot version will probably offer a lot of new lighting & shaders possibilities as well.