  The accretion disk around a black hole and its emissions play an essential
role in theoretical analysis of the black hole image. In the literature, two
analytical toy models of accretions are widely adopted: the spherical model and
the thin disk model. They are different geometrically but both thin optically.
We polish them for free-falling accretions around static spherical black holes.
As an application, we investigate the image of a class of nonsingular black
holes conformally related to the Schwarzschild black hole, which are the vacuum
solution of a family of conformal gravity theories. Results are compared with
the Schwarzschild black hole of the same mass. Our results indicate that the
conformal factor does not affect the shadow radius seen by distant observers,
but it leaves an imprint on the intensity image of black hole.
