Great-looking tank! I'm sure that you've found plants already, but if you're looking for a floater, try either a dwarf lily (they grow fast and put up tons of lilypads if you let them) or the old classic, hornwort, it's quite adaptable and can be found either native or invasive almost everywhere in the world.
Blackwater & Aquatic Botanical Enthusiast
35 Gallon SE Asian-themed Blackwater Biotope: 1x Betta splendens, 8x kuhli loaches, 9x neocaridina sp., 1x rabbit snail
20 Gallon Tall Tinted Escargotoire: 6x Apple Snails, 14x White Cloud Mountain Minnows