We present a family of rank-symmetric diamond-colored distributive lattices that are
naturally related to the Fibonacci sequence and some of its generalizations. These lattices
reinterpret and unify descriptions of some uncolored or differently colored lattices found
variously in the literature. We demonstrate that our symmetric Fibonaccian lattices
naturally realize certain (often reducible) representations of the special linear Lie algebras,
with weight basis vectors realized as lattice elements and Lie algebra generators acting
along the covering digraph edges of each lattice. We present evidence that each such
weight basis possesses certain distinctive extremal properties. We provide new descriptions
of the lattice cardinalities and rank-generating functions and offer several conjectures and
open problems. Throughout, we make connections with integer sequences from the OEIS.