Have your thought about dwarf hairgrass, could give it a nice natural carpet.
I have and there are a very few runners of it in the middle of the s. repens and Lilaeopsis brasiliensis, which carpets just the same growth wise as DHG. First tank with it in there, since it has no fish, the fish wouldn't let it stay planted in my big tank. Hoping it will carpet well so I can also use it in other tanks. DHG grows really, really slow for us since we don't use Co2.
The front area is basically a trial to see which of the 3 carpet plants grow faster. There is also a sprig of brown hygro that for whatever reason grows on the substrate and crawls instead of growing upwards, This would also make a very lovely carpet in a tank, so seeing if the higher light of this tank makes it change it's growth pattern.
Plant list for this tank is -
3 crypts - mioya, wendtii, nevelli?
rotala sp. green
Dwarf green hygro
Undecided what I am going to pull out to put my Vesuvius sword plantlet in, but this tank si basically just a grow out and will change plant frequently as the mood strikes me.