  We study the optical appearance of a thin accretion disk around compact
objects within the Einstein-Gauss-Bonnet gravity. Considering static
spherically symmetric black holes and naked singularities we search for
characteristic signatures which can arise in the observable images due to the
modification of general relativity. While the images of the Gauss-Bonnet black
holes closely resemble the Schwarzschild black hole, naked singularities
possess a distinctive feature. A series of bright rings are formed in the
central part of the images with observable radiation $10^3$ times larger than
the rest of the flux making them observationally significant. We elucidate the
physical mechanism, which causes the appearance of the central rings, showing
that the image is determined by the light ring structure of the spacetime. In a
certain region of the parametric space the Gauss-Bonnet naked singularities
possess a stable and an unstable light ring. In addition the gravitational
field becomes repulsive in a certain neighbourhood of the singularity. This
combination of features leads to the formation of the central rings implying
that the effect is not specific for the Einstein-Gauss-Bonnet gravity but would
also appear for any other compact object with the same characteristics of the
photon dynamics.

General Relativity and Quantum Cosmology;High Energy Astrophysical Phenomena