  We study exciton-polaritons in a two-dimensional Lieb lattice of
micropillars. The energy spectrum of the system features two flat bands formed
from $S$ and $P_{x,y}$ photonic orbitals, into which we trigger bosonic
condensation under high power excitation. The symmetry of the orbital wave
functions combined with photonic spin-orbit coupling gives rise to emission
patterns with pseudospin texture in the flat band condensates. Our work shows
the potential of polariton lattices for emulating flat band Hamiltonians with
spin-orbit coupling, orbital degrees of freedom and interactions.
