We have extended a simple model of nonlinear diffusive shock acceleration to include the injection and acceleration of electrons and the production of photons from bremsstrahlung, synchrotron, inverse-Compton, and pion-decay processes. We argue that the results of this model, which is simpler to use than more elaborate ones, offer a significant improvement over test-particle, power-law spectra which are often used in astrophysical applications of diffusive shock acceleration. With an evolutionary supernova remnant (SNR) model to obtain shock parameters as functions of ambient interstellar medium parameters and time, we predict broadband continuum photon emission from supernova remnants in general, and SN 1006 in particular, showing that our results compare well with the more complete time-dependent and spherically symmetric nonlinear model of Berezhko, Ksenofontov, & Petukhov. We discuss the implications nonlinear shock acceleration has for X-ray line emission and use our model to describe how ambient conditions determine the TeV/radio flux ratio, an important parameter for -ray observations of radio SNRs.