A shade garden is one that gets about 4 hours or less of direct sun
A part shade garden is one that gets more than 4 hours of direct sun but less than 6 hours of direct sun anything over that is a sun garden.

With any garden there will be some spots that get more sun than others. That is the spot you should plant those that require a little more sun.

If you have the room dogwood is a shade lover. It grows 5 to 6 feet tall and there are some with lovely foliage. Yew or cedar do well in part shade. Annabell Hydrangea is hardy and does well in part shade too.

If you can get it Bleeding heart luxuriant blooms all summer with small pink flowers and once established will be about the height of your Astilbe. It is very hardy and you can put it in any light conditions. I have a plant in the dapled shade of a tree and one in full sun and they do equally well.

Well that's all I can think of right now. It sounds like you will have a lovely flower bed

Thanks for the response dowling, and the compliment. I do have room for dogwoods and actually planted 3 this spring, I do like them and its good to know they like shade, one of mine is in full sun, guess I should move it. . .

I would say this is probably a part shade bed, as it gets direct sun in both the morning and early evening til the sun sets and that will increase as the days get longer. Thanks for explaining the difference, I knew what full sun meant but was not sure what consituted part shade, that opens up a whole lot more choices. . .

Try monkshood, purple sensation allium, hydrangea, lobelia cardinalis , goatsbeard, spirea, viburnum, japanese maple,

more tall perennial suggestions:
crocosmia Lucifer
Japanese anemone
meadowrue, Thalictrim

find a native flowering/fruiting shrub or tree in your area to attract birds

add a bubbling fountain or bird bath

Remember on the other side of a fence can be a cold pocket especially on the north. Do not feed them after August. Mulch well to overwinter them. Hosta & Astilbe will do fine. Lamium might not, but usually bounces back from roots. Several plants with snow on mtn common name, so not sure which one. I hope you didn't plant Aegopodium podagraria 'Variegatum' because it is a spreading thug only suitable for a place by itself. I've removed it from a garden when I realized the spring planting was a bad idea. I do have it in another area and have to keep an eye out for blooms to prevent reseeding and shovel prune the edges to keep it in bounds.

Another way to give height is to mound the bed or add graduated size boxes made from fence wood. The center would be tallest and can be offset. If your bed is 5-6 feet wide you won't be able to mound it much, but some helps. I try to middle mound all my beds for that berm effect that I prefer.