Pothos are pretty adaptable, but it will vine out to lighter areas and won't be as bushy in the shade. Shady spots are great places for silk foliage. Check online vendors for larger sized artificial plants (the artificials offered by the usual pet vendors are pretty small). You could buy several "sprigs" of something and bundle them together.
Rapsis or parlor palms are a bit pricier, but would fit the bill. It's hard to make recomendations, without knowing just how dimly lit the cage is. Chinese evergreen, pteris ferns, gunmetal palms, and a few other plants take pretty dense shade, well. Apidestra or cast iron plant is another.