I think it would be nice if we were able to use normal maps with lights.
It could add some 3D lit and depth to our sprites.
Here is a gif demonstrating the difference between a flat texture sprite and one using normal map;
As to where to setup normal map in the editor. I think it could be a normal map light behaviour attached to sprite objects which would be like a normal animation editor except we can not add our own frames and animations, it would copy the animation properties of the object and allow us to setup a normal map for each frame of the sprite object as usual
So if a sprite object had 2 animations and each animation 2 frames, the behaviour would allow me to setup normal maps for those 2 animations and 2 frames.