Then you may want to look for a couple of plants with big, bold leaves to create structural interest. Some leaves are very intricate - like most ferns. Some are quite simple, like the oval, slightly pointed leaves of the dogwood. Others are tiny and quite dainty - like the many nepetas and campanulas, or Veronica peduncularis 'Georgia Blue'. Then you have the spiky ones - yuccas, bearded irises and kniphofia to name a few.
Many grasses grow erectly, but others flow outward in a graceful vase or fountain shape.
Some form perfectly rounded mounds. A few, like hakonechloa cascade forward almost like waves crashing on the shore. Many bulbs, such as bearded irises and daylilies will give you a fan shape, like a row of broad and slightly tipsy exclamation points. The dissectum type of Japanese maples also have that weeping, forward flowing form along with a very lacy texture. Both are perfect for hiding the yellowing foliage of spring bulbs, too, as they won't really get growing until the bulbs are done.