  We investigate the ion distribution and overcharging at charged interfaces
with dielectric inhomogeneities in the presence of asymmetric electrolytes
containing polyvalent and monovalent ions. We formulate an effective "dressed
counterion" approach by integrating out the monovalent salt degrees of freedom
and show that it agrees with results of explicit Monte-Carlo simulations. We
then apply the dressed counterion approach within the framework of the
strong-coupling theory, valid for polyvalent ions at low concentrations, which
enables an analytical description for salt effects as well as dielectric
inhomogeneities in the limit of strong Coulomb interactions on a systematic
level. Limitations and applicability of this theory are examined by comparing
the results with simulations.
