Since you are gardening in pots you can be completely flexible. Grow anything you like the look of. The available light under the other plants won’t be much affected by the larger plants since you can adjust their positions. I would remove the plastic and labels from the pots as it detracts from their appearance. More in my view than fallen petals, and I wouldn’t describe either Impatiens or Pelargoniums as ‘prolific‘ shedders. However, foliage Begonias might suit you.

I grew coral bells under mine! beautiful foliage and flowers in summer.

Baby tears gives a nice cool moss look. Or Cymbalaria..adds flowers and is a tough groundcover. Both also take the water the Elephant ears thrive in.

Coleus ? i have lime green but they come in a wide variety of colors.