Microscopic thin films have shown wavelength selectivity in the context of radiative heat transfer. We propose a methodology to shift the wavelength selectivity in the desired location. This work deals with the far-field and near-field radiation from thin films embedded with nanoparticles. The calculations of emission spectra are performed using the Fresnel equations in the far-field limit, and using the dyadic Green's function formalism for transmissivity between the closely spaced objects in the near-field regime. For the media doped with nanoparticles, an effective dielectric function using the Maxwell-Garnett-Mie theory is used to calculate emissivity and radiative heat transfer. It has been shown that the wavelength selectivity in the emission spectra can be influenced by varying the size and/or the volume fraction of nanoparticles. We characterize the wavelength selectivity using real and imaginary parts of the effective refractive index. We show that the influence of nanoparticles on wavelength selectivity is different depending on whether the particles are of polar materials or are metallic.