Bog plants are NOT going to be 'easy care'. I think it'd be expensive getting enough to fill such a big planter.
You could fill it with decent potting mix and plant a variety of tropicals. The large volume of soil 'might' make for good conditions as long as you don't drown the plants. Elephant ears are one plant I have grown and think does cope well with wet feet. They would make a large striking display, do you have room for top growth up to four or five feet? Surround the elephant ear(s) with a few pothos, or other basic easy plants, and you could have a big planter such as shopping malls do.
Easy plants: Pothos, Aglaonema, Dracaena, Tradescantia (wandering jew/inch plant). If you have a Home depot or Walmart with any kind of indoor plants, you can find these. Elephant ear may have to be mail ordered. I think you could have fun with this plan.
