We show that if a flavorless vector meson remains bound after deconfinement, and if its limiting velocity in the quark-gluon plasma is subluminal, then this meson produces a distinct peak in the spectrum of thermal photons emitted by the plasma. We also demonstrate that this effect is a universal property of all strongly coupled, large- N c plasmas with a gravity dual. For the J / ψ , the corresponding peak lies between 3 and 5 GeV and could be observed in heavy-ion collisions at the LHC.