Yeah, Cryptocorynes are a good idea! I love the ones that have a red leaf underside. I used to have tons in my tank years ago, but they got invasive and I pulled them all up

and planted more. But they never have time to grow, the big catfish destroys everything. My tank will be nearly plantless until the stupid fish dies, in a decade or so. Maybe I'll try Java ferns, apparently that fish doesn't destroy those as much.
Or anubias would look nice, the flowers are excellent! Mine bloom underwater, but sometimes a spike makes it to the surface. They are hardy plants, slow growers though, and love to be mounted on driftwood.
I'm getting really excited about your pond design!!