  In this study, we focus on a static spherically symmetric $f(R)$ black hole
spacetime characterized by a linear dark matter-related parameter. Our
investigation delves into understanding the influence of different assumed
values of this parameter on the observable characteristics of the black hole.
To fulfill this task, we investigate the light deflection angles, which are
inferred from direct analytical calculations of null geodesics.} To examine the
black hole's properties further, we assume an optically thin accretion disk and
explore various emission profiles. Additionally, we investigate the shadow cast
by the illuminated black hole when affected by the disk. Furthermore, we
simulate the brightness of an infalling spherical accretion in the context of
silhouette imaging for the black hole. Our findings indicate that, except for
some specific cases, the observed brightness of the accretion disk
predominantly arises from direct emission, rather than lensing and photon
rings. Moreover, we reveal that the linear dark parameter of the black hole
significantly influences the shadow size and brightness. Our discussion covers
both analytical and numerical approaches, and we utilize ray-tracing methods to
produce accurate visualizations.
