I almost feel like a hypocrite for saying this (my first paludarium was a 10-gallon, with a bunch of lava rocks siliconed all over the place), but I really think you should consider getting a bigger tank.
a 10 gallon isn't a very good beginner tank, and even less so if someone is looking to do a riparium/paludarium set up. For the typical set up, you just up and 1/2 your available volume by setting it up as a paludarium. On top of that, you can shave another 25-30% off of the remaining volume due to backdrop/hardscape and what not.
Granted, the terrestrial plants drawing nutrients from the water column will cover a lot of the filtration you need, but there is still a minimum space requirement necessary for a lot of critters.
I'd strongly urge you to at least use a 29 gallon, they are still relatively inexpensive, and will offer a lot more room both for scaping and for the inhabitant's comfort.
Anyways, aside from that...
I tend to like creeping ficus, but it can really grow, and is probably better in larger tanks. something like selaginella (sp?) or baby's tears can do well in a moist substrate, but I don't have much experience using either one in paludariums. most aquatic mosses will also grow over exposed rocks/wood/whatever if they can keep their feet damp. this is probably your best option for that sized set-up. Almost anything else will require near religious trimming , or it probably won't work at that scale.
Also, within something the size of a 10-gallon, I wouldn't worry too much about your choice of substrate, likely everything will draw it's nutrients straight from the water-column. probably anything relatively inert, and somewhat porous will work well (lava rock, pumice, flourite, kitty litter, safe-t-sorb, oil-dry, etc.) anything that works well for hydroponics will likely work for this. you more or less just want to give the plant something to support it's root structure.
If you stick to smaller critters, it may work, but I'd be hesitant to put much anything bigger then a typical feeder guppy in it.