  The Event Horizon Telescope collaboration has revealed the first direct image
of a black hole, as per the shadow of a Kerr black hole of general relativity.
However, other Kerr-like rotating black holes of modified gravity theories
cannot be ignored, and they are essential as they offer an arena in which these
theories can be tested through astrophysical observation. This motivates us to
investigate asymptotically de Sitter rotating black holes wherein interpreting
the cosmological constant $\Lambda$ as the vacuum energy leads to a deformation
in the vicinity of a black hole -- new Kerr--de Sitter solution, which has a
richer geometric structure than the original one. We derive an analytical
formula necessary for the shadow of the new Kerr--de Sitter black holes and
then visualize the shadow of black holes for various parameters for an observer
at given coordinates $(r_0, \theta_0)$ in the domain $(r_0,\; r_c)$ and
estimate the cosmological constant $\Lambda$ from its shadow observables. The
shadow observables of the new Kerr--de Sitter black holes significantly deviate
from the corresponding observables of the Kerr--de Sitter black hole over an
appreciable range of the parameter space. Interestingly, we find a finite
parameter space for ($\Lambda$, $a$) where the observables of the two black
holes are indistinguishable.
