Answer: There are literally thousands and thousands of plants to choose from! You might visit some neighbors' gardens, botanical gardens, and/or your library (to find some books with photos) to see what suits your fancy. Off the top of my head, I'll suggest a few ideas--but please do research the huge range of options you have!
My hunch is that you are a new gardener, so I suggest starting with some reliable plants. You may not want to plant the whole area this first year--just get a feel for your soil, temperatures, shade patterns, etc. A mix of flowering shrubs, evergreen bushes, and perennials would be nice.
A few shrubs: butterfly bush (Buddleia davidii), viburnum, dwarf boxwood (evergreen, non-flowering)
Perennials: artemisia, asters, coreopsis, bearded iris, peonies, phlox, salvia, speedwell, Shasta daisy, coneflowers
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