Depends somewhat on what you personally consider "big" and where in the tank you plan on having them (planted in the bottom or mounted for instance). How much light you will provide will be a factor as well as whether you mind doing some serious pruning.
Taargus, doesn't the H. arifolia have a spread of about a foot? Depending what all Rball wants to put in there, could be too large for what he is looking for.
There are some fairly small broms though most do need some decent lighting. If you have the tank brightly lit, there are some mini AVs that can be used to add color. Then there are Cryptanthus which can be used to color things up but, again, they need bright light. If you want something in the more "mini" range, there is Epipremnum 'Pincushion' -- a relative of pothos but it has a clumping habit instead of vining. For me it generally maxes out at about 3" tall. Downside is that it is a slow grower so it tends to be a bit more on the expensive side. Then there is a type of Selaginella (think it might be S. apoda ... been years since I last had it) that has a clumping habit. You could also try Ludsia discolor. If you planted it pot and all, you might be able to utilize Ficus pumila ... though that definitely needs some fairly bright light to do well.
