Hornwart is good -- just make sure it's accessible, because in low light it'll grow rapidly towards the light and eventually cover half the water surface.

It's a good plant to have, though, because it puts out some kind of chemical that prevents blue-green algae from growing.
I got a couple of the 'umbrella' and variated sword plants from PetSmart that come in the tube. The swords have barely hung in there, but the umbrella plants have done great. My otto loves to hang out on them.
I'd say I have about a 60/40% mixture of artificial to live plants in my 10g, and it works fairly well to give a nice aquascape.