  We model the light-curves from radiation-driven clouds near an accreting
black hole. Taking into account the multiple images due to strong gravitational
lensing, we find that sharp spikes can significantly enhance the observed flux.
Following our previous work (Horak & Karas 2006a,b) we assume that scattering
of ambient light takes place in a cloud that is in radial motion under a
combined influence of black hole gravity and the radiation field. The
retro-lensed photons give rise to peaks in the observed signal that follow with
a characteristic time lag after the direct-image photons. Duration of these
features is very short and the predicted polarization varies abruptly on the
time-scale comparable with the light-crossing time of the system -- a signature
of the photon orbit. We also consider the polarization properties of scattered
light.
