Would help to know what types of plants you have in your tank right now. (To get color contrasts, sizes, etc.)
My 75 gal is also 24" high, and I've got Hygros easily (and quickly) growing to at least
20" height, but the'd get even taller if I didn't trim them every week or two.
I love Amazon Swords as well, along with Ludwigia, Lotuses for mid-level and color, and varieties of Aponogeton.
I second the hygro. I have tiger hygro in a low-tech 36 gallon and it easily reaches the surface. Crypt balansae is supposed to grow incredibly tall too and it has very pretty narrow slightly wavy leaves.
One of my favorites was always pogostemon stellatus I believe it is. It grew out of the top of my 24" tank when I was going high tech. I eventually decided all the stem trimming was too much. However it was really beautiful and easy to grow.