The standard Pothos can be planted up high and allowed to trail downwards. Or it can be planted on the bottom of your tank and will climb up on it's own, even up glass. I find the leaves get much bigger when allowed to climb instead of hang.
The vine kinds of philodendrons can be used as trailers or will also climb straight up glass. But the usual walmart ones (here anyway- you may have more selection) usually have smaller leaves than a pothos.
Various ivys are often available at walmart and can grow up or down, or be trained to do just about anything. These usually have pretty small leaves though (still good for cover).