An Ideal spot for Begonias, New guinea Impatiens or you could even try Regular Impatiens.

I like Go-Go or Nonstop Begonias. Both have lovely rose shaped flowers that average 2 1/2 to 3 inches across. They are the only flower I know of that has distinguishible male and female blossoms. The male is roselike and the female is single. They have a tuber which can be saved and grown another year.

If you want a shrub--try Dogwood
Perennials of different heights include

Bleeding heart--bleeding heart luxuriant has smaller heart shaped flowers, minus the drop, but it blooms all summer if it gets enough moisture.
Astilbe--lovely plumes in various colors
Hosta--It comes in many Heights,shades of green and bicolors with different flowers