A couple of quotes from papers that have shown up recently: from: http://arxiv.org/pdf/1512.05327.pdf We consider several models for these fermions, including a single vector-like charge 2/3 T quark, a doublet of vector-like quarks (T, B), and a vectorlike generation including leptons that also contribute to the X → γγ decay amplitude. from: http://arxiv.org/pdf/1512.05326.pdf Models of a scalar resonance which explain the excess can come from sectors with a wide variety of field content and quantum number assignments . The simplest possibility which avoids many correlated bounds is a resonance that is a singlet under the Standard Model gauge group. This implies that the coupling to protons and photons is generated by loops of new non-Standard Model particles that are colored and charged ... The most economical model consists of adding a single pair of colored and hypercharged fermions, thus providing for loop-level couplings to gluons and photons.