Make image glow independently

I have a 2D PNG image I am using as a background piece in a scene. I don’t want its lighting to influence anything else in the scene, or any of the lights in the scene to influence it. I just want it to appear, exactly as it would appear in Photoshop, etc., in the scene.

How do I make it appear that way in the render?

You can use “alpha over” in the compositor:

You can use this for mixing “render layers” and different scenes too.