Metal-Insulator-Metal (MIM) nanostructures provide tunable multiple absorption/emission peaks desirable for spectroscopy, light sensing and thermophotovoltaic (TPV) applications. The efficiency of TPV systems can be improved by employing MIM emitters with resonators that allow high emission above PV cell bandgap and low emission elsewhere. Although there have been attempts to design MIM emitters for TPV systems, a comprehensive study that investigates and optimizes different resonator shapes is lacking. In this study, broadband TPV emitters with W-SiO2-W nanostructures are optimized for pairing with GaSb PV cells. A numerical approach is followed utilizing finite-difference time-domain method and particle swarm optimization scheme, MIM emitters with four resonator shapes: disk, square, pyramid, and cone are dimensionally optimized to attain an emissivity spectrum that overlaps with high quantum efficiency region of the GaSb cell. The optimized emitters are compared for efficiency, power output, material consumption, as well as their optical response to temperature and angular effects. At an emitter temperature of 1600 K, electrical power outputs of 2.335-2.418 W·cm-2 and spectral efficiencies of 56.2-57.6% are obtained. It is found that flat resonators tend to achieve similar performance to that of pointy resonators with shorter heights. Among the considered shapes, disk emitter demonstrates the highest efficiency with minimum material consumption. Compared to a plain W emitter at the same temperature, the disk MIM emitter exhibits significantly higher spectral efficiency and electrical power output (34% and 215% respectively). The results demonstrate the successful use of nano-elements in TPV systems, and the potential for fabricating and realizing such structures.