If you have plenty of branches and in the cage, a pothos is hard to beat. For $15 or less you can obtain a full hanging pot and place the pot at the age bottom and drape the vines wherever you'd like, in order to provide cover, drinking sites, and a satisfactory visual appearance. Your options are innumerable, depending on your lighting and watering methods, size of cage, and green thumb. Most people use ficus benjamina or Schefflera, hibiscus is too light hungry for most cages, but many try it, parlor or Bella palms, cissus, china doll, aralia or false aralia, even thornless citrus trees.