  Collaborative international efforts under the name of the Event Horizon
Telescope project, using sub- mm very long baseline interferometry, are soon
expected to provide the first images of the shadow cast by the candidate
supermassive black hole in our Galactic center, Sagittarius A*. Observations of
this shadow would provide direct evidence of the existence of astrophysical
black holes. Although it is expected that astrophysical black holes are
described by the axisymmetric Kerr solution, there also exist many other black
hole solutions, both in general relativity and in other theories of gravity,
which cannot presently be ruled out. To this end, we present calculations of
black hole shadow images from various metric theories of gravity as described
by our recent work on a general parameterisation of axisymmetric black holes
[R. Konoplya, L. Rezzolla and A. Zhidenko, Phys. Rev. D 93, 064015 (2016)]. An
algorithm to perform general ray-tracing calculations for any metric theory of
gravity is first outlined and then employed to demonstrate that even for
extremal metric deformation parameters of various black hole spacetimes, this
parameterisation is both robust and rapidly convergent to the correct solution.
