Ficus, schefflera, and pothos are all plants I would use and recommend. Over time they will grow to really fill up your cage. You can use 65k lights to help them grow, and use a fast draining soil mixture comprised mostly of sand or a mix of small rocks and top soil to get that water out quickly, because with all the moisture they are receiving in that cage it becomes very easy to get root rot.
If you get your plants at a place like Lowes, Walmart, etc. you can get them much cheaper than at a place like a florists. Just make sure to change out the soil and wash the plant roots off because more than likely the soil will have fertilizer in it.