I use Rhododendrum for a backdrop. Beautiful flowers in spring and nice foliage the rest of the season. Based on your zone I would recommend PJM Rhodo's.

sorry spelled wrong 'Rhododendron'

I have Anabelle hydrangea in the back of one part of my garden. 2nd year, doing ok so far. Too early to tell if they're going to bloom. Might be too shady.

I also have Goatsbeard... it's a woody perennial, so it does die to the ground, but it bounces back quickly in the spring.

I've found boxwoods do just fine in shade with dappled sun, particularly Green Velvet (low mounding, slow grower, minimal maintenance)...and Green Mountain (natural conical shape). Google for yourself and check the zones. You're more north than me.

One I LOVE for shade is Buckthorn Fine Line. Grows in sun or shade. This one has a tree shape with feathery, flowy, tropical-looking foliage. Google this one too.

Gayle

I use Chelone/Turtleshead. While not a shrub it does have the height and structure that I wanted at the back of the bed and has these bright hot pink flowers at the tips. Love the contrast with the foliage of the hosta.

I also have astilbe tucked in here and there. The Goats Beard has a nice white foamy quality to the blooms.

'Little Henry' Sweetspire, 'Sky Pencil' Holly, 'Lemon Daddy' Hydrangea, 'Othello' Ligularia are a few I have that do well in some shade.

What is the light in the back? If filtered or part shade, take a look at yellow waxbells. Hot afternoon sun would be a problem; and in deep shade it may not get tall enough.

Has a shrub feel. Dies back to the ground. Listed as zone 5, but I bought it from someone that had planting in my zone (4a) and it was outstanding.

Late summer bloomer.

I also like Turtleshead for the late bloom and height.

If area gets some sun check out Sutherland Gold (Elderberry).

Paul

I have huge ferns among my hostas. The ferns were there first, actually, and were the only thing on the north side of the house before the hostas got put it. They are Interrupted Fern,Osmunda claytoniana, and supposedly grow 2 to 4 feet tall, but mine are well over 4 feet, maybe because they are old (over 25 years). They are upright growers, but the outside fronds do flop over by mid-summer; where they cross the path, I cut them back, and leave the others arching over the hostas.

Many viburnum can handle shade. Oakleaf hydrangea far surpass any of the other types IMHO for structure, size and multi-season interest. I use 'snow queen' for upright blooms and growth habit. Calycanthus can also handle a decent amount of shade. Columnar yews would also be cool for a backdrop

I have a tall toad lily that gets over 3 feet tall and acts like a shrub too. So does goatsbeard.

Ajfan... While I am sure that some of these suggestions are great ones, be sure to check individual varieties for hardiness in your zone. For instance, Oak Leaf Hydrangea is not hardy in zone 4.

A comment on yews in shade: They get pretty scraggly... they never really form a good "screen" or get much height. The previous owners had planted some at the back property line, in hopes to screen the rear neighbors. They were pretty pathetic. Same with Dogwoods and Burning Bush. They can tolerate shade, but they never look that great.

ok, ignore everything I said but viburnum. They are hardy and don't get scraggly. lol