The impact of quantum effects and thermal fluctuations on properties of small lithium clusters, Li-8 and Li-20, is investigated at low temperatures with ab initio path integrals. The static optimized structures, i.e., the minima of the potential energy surface, are characterized by packings of multicenter bonded tetrahedral building blocks featuring short and long Li-Li bonds. Quantum effects at 10 K are found to be induced by zero-point motion, whereas tunneling turns out to be irrelevant. The simulations uncover that these quantum effects destroy the distinction between short and long chemical bonds, while preserving the overall structural shape of the clusters.