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In this paper, by taking the accretions into account, the observationalshadows and rings casted by the Brane-world black hole are numericallyinvestigated when the observer located at the cosmological horizon. The resultshere show that the radius $r_p$ of photon sphere increased with cosmologicalparameter $\alpha$ and dark matter parameter $\beta$, while the impactparameter $b_p$ decreased with $\alpha$ and increased with $\beta$. For thethin-disk accretion, it turns out that the total observed intensity are mainlycomposed of the direct emission, while lensing ring and photon ring onlycontribute a small contribution and a negligible contribution, respectively.And, we find that shadow and rings exhibit some different and interestingfeatures when the disk located at different positions. For the static andinfalling spherical accretions, it is obvious that the size of shadow is alwaysthe same for both accretions, which means that shadow is only related to thegeometry of space time in this case. The luminosity of shadow and photon sphereare closely related to the Doppler effect and the emissivity per unit volume$j({\nu_e})$. In addition, the influence of dark matter and cosmologicalconstant on observed intensity of shadows and rings are carefully emphasizedthroughout of this paper. Finally, we obtained the burring images of shadowsand rings by using the nominal resolution of the Event Horizon Telescope, andstudied the upper limits on the X-clod dark matter parameter $\beta$ with theaid of the data of the shadow of M87.

Effect of dark matter on shadows and rings of a brane-world black hole illuminated by various accretions