  Thermal photon emission is widely believed to reflect properties of the
earliest, hottest evolution stage of the medium created in ultra-relativistic
heavy-ion collisions. Previous computations of photon emission have been
carried out using a hydrodynamical medium description with smooth, averaged
initial conditions. Recently, more sophisticated hydrodynamical models which
calculate observables by averaging over many evolutions with event-by-event
fluctuating initial conditions (IC) have been developed. Given their direct
connection to the early time dynamics, thermal photon emission appears an ideal
observable to probe fluctuations in the medium initial state. In this work, we
demonstrate that including fluctuations in the IC may lead to an enhancement of
the thermal photon yield of about a factor of 2 in the region $2 < p_T < 4$
GeV/$c$ (where thermal photon production dominates the direct photon yield)
compared to a scenario using smooth, averaged IC. Consequently, a much better
agreement with PHENIX data is found. This can be understood in terms of the
strong temperature dependence of thermal photon production, translating into a
sensitivity to the presence of 'hotspots' in an event and thus establishing
thermal photons as a suitable probe to characterize IC fluctuations.
