  The effects of image charges (i.e., induced surface charges of polarization)
in spherical geometry and their implication for charged colloidal systems are
investigated. We study analytically and exactly a single microion interacting
with a dielectric sphere and discuss the similarities and discrepancies with
the case of a planar interface. By means of extensive Monte Carlo (MC)
simulations, we study within the framework of the primitive model the effects
of image charges on the structure of the electrical double layer. Salt-free
environment as well as salty solutions are considered. A remarkable finding of
this study is that the position of the maximum in the counterion density
(appearing at moderately surface charge density) remains quasi-identical,
regardless of the counterion valence and the salt content, to that obtained
within the \textit{single}-counterion system.
