  We study the propagation of structured optical scalar beams in a spacetime
background parameterized by a second-rank symmetric tensor. An analytic
expression for the Green's function in a cylindrical coordinate system is
obtained for particular choices of such a tensor. This facilitates the
numerical exploration of the propagation of apertured Gaussian beams in this
nontrivial background. Unusual focusing properties are found along with a
decrease in the Gouy phase compared to that in standard vacuum. In the case of
apertured Bessel beams, the medium allows to overcome finite aperture effects
so that the corresponding diffraction length is increased; besides, the central
spot of a zero order Bessel concentrates an increased fraction of the energy of
the beam. Multiple scenarios beyond an electromagnetic field in the presence of
an anisotropic medium could support the results reported here. They include a
bosonic field in a weak gravitational field or a nontrivial spacetime
background arising from Lorentz symmetry breaking. In particular, our results
could illustrate how optically transparent multiferroic materials offer
unprecedented opportunities to tailor structured beam propagation, as well as
to simulate nontrivial spacetime backgrounds.
