Extract a 2D shadow pass from 3D for 2d manipulation. Or project soft shadows back into a 3D scene for use with the OpenGL renderer.
Bump maps and height maps can be used to simulate 3D displacement in materials. Use it to create rough textures and fine depth detail surfaces without the need to use an extreme number of subdivisions.
Use Camera Projection, attach images to 3D objects or use Image Plane 3D. Learn about the differences and apply the correct method in DaVinci Resolve & Fusion.