Any size tank is suitable for planted landscape, check out the stuff on www.aquabotanic.com and look at some of the tank volumes...you will be amazed at how beautiful small tanks can look with appropriate scale.
Thanks much, I'm happy with it! And this is actually a low-light set-up at 2 wpg. The reddish plant is a red wendtii crypt. Those buggers will grow in pretty low light if you want a splash of color. With smaller set-ups, you just need to keep crypts groomed so they don't overtake the tank.