Textured 2D Plane with Depth

I’m starting to prototype a game with a Paper Mario art style, with textured 2D planes. It looks alright, however, I would like said elements to have little depth to them, like the thickness of cardboard. Is there a way to do this through via materials? I really don’t want to make 3d models the shapes of trees, rocks, etc., when it’s so easy to just slap a PNG onto a plane.