Here are some plants that you might find of interest:
Aquatic:
mosaic plant
duckweed (very invasive in most areas - DO NOT throw out in the trash- should be burned.)
Java fern
parrots feather
Terrestrial:
dwarf mondo grass
Japanese rush plant - Acorus pussilus (and other varieties of Acorus) It has a nice grass look to it.
Arrowhead plants
Aquatic "Sword plants" also do very well when grown in moist areas. They have a different look to them than when they are grown submersed, but they still look great.
pothos (over-rated in my opinion... it is everywhere! lol but is great plant- I still have some in one of my vives.)
MOSS MOSS and MOSS!!! <3
Java moss and riccia are both nice looking and can do well in both the aquatic and terrestial areas (as long as they are kept moist).
Here: this link will give you more ideas. Basically a riparium is the same as a paludarium (please no bashing from the dictionaryists lol).
hydrophytesblog.com
If you have a hard time finding a plant you like, try posting a want add at herp and aquarium forums, post a thread on craigslist, or check ebay and other sites. You should be able to get these plants fairly cheap. Or you can ask around here too

I'm sure someone wouldn't mind giving you some of their pothos snippings lol