  Inspired by recent experiments on the Sr-doped nickelates,
$La_{2-x}Sr_xNiO_4$, we propose a minimal microscopic model capable to describe
the variety of the observed quasi-static charge/lattice modulations and the
resulting magnetic and electronic-transport anomalies. Analyzing the motion of
low-spin (s=1/2) holes in a high-spin (S=1) background as well as their their
coupling to the in-plane oxygen phonon modes, we construct a sort of
generalized Holstein t-J Hamiltonian for the $NiO_2$ planes, which contains
besides the rather complex ``composite-hole'' hopping part non-local spin-spin
and hole-phonon interaction terms.
