CC Cylinder or CC Sphere. Set the render mode to inside only, make them huge.
But I understand you can´t use CC Cylinder or CC Sphere in a 3D project, or?
Can you somehow make a camera that can move inside a sphere where the image act an outside wall?
Yes. Both plugins respond to the After Effects camera in 3D space, so you can position your camera "inside" the Sphere or Cylinder. But note Mylenium's advice to set it to render "Inside Only".
Alternately, you can break your background into segments and orient them so you have a series of flat planes instead of a true curve, which often works well enough.
Or, investigate Trapcode Horizon.