When I work with camera I set the light like in a room.
If I want to have an image in that room that has it´s normal look and light can I somehow make so the 3D light does not effect that image?
No, AE doesn't support light exclusions. You will have to use 2 separate 3D comps, but combine them as 2D in teh parent comp. You need to link the cameras with expressions across both comps... On second thought you could also try applying a layer style to your picture. Layer styles break 3D rendering order, so this layer would not show any response to light, but it may just as well have other side effects on your other layers. Really depends on teh specific scene setup.