  The composition of ultra-high energy (UHE) cosmic rays E>10^17 eV is still
unknown. The observation of UHE photons would extend the observed
electromagnetic spectrum to highest energy and open a new channel for
multimessenger observations in the universe. Current limits on the photon flux
already constrain ``exotic'' scenarios where a large number of photons is
expected by the decay products of supermassive X-particles. Motivated by the
growing exposure of UHE cosmic ray experiments - like the Pierre Auger
Observatory - the observation of conventionally produced GZK photons may be in
reach in the near future. We investigate UHE particle propagation using the
Monte Carlo code CRPropa. Particularly, the expected photon fluxes normalized
to current experiments as well as prospects for future experiments are
illustrated. Varying source and propagation scenarios are analyzed and the
impact on secondary GZK photons is shown. For the specific case of Centaurus A,
we study which source parameters can be tested by searching for the expected
GZK photons.
