I've always been surprised to see what Home Depot and Lowe's have. Usually pretty nice broms, and other tropical plants that look real nice are are fairly cheap. Also check out your local nursery I've found some really nice plants there and they are also pretty cheap. I even got lucky one time and found some nice plants mostly broms and some ferns at Walmart on clearance.
Some of my favorites are:
Creeping Wirevine it's the one with the tiny little leaves. It might be an annual so you might have to replant it but I think it looks real nice.
Fittonia there is another thread that talks about a variety that has pink veins rather than white. Personally I like the white.
And Broms I have at least three varieties in my viv this is my favorite. It started out the size of a nickle and now is almost the size of my hand. The nice thing about broms is that you can mount them about anywhere. This one is just siliconed to the stick it is sitting on.
All of these I bought at one of the places I mentioned before for under $3. I have been pretty pleased.