I spent the day earlier working on my mixed bed of hydrangeas.
I have mine planted with two clumps of peonies, some bleeding heart, Euonymous japonica (not sure of hardiness to your zone for this one), and a variety of hardy ferns (Christmas, Cinnamon, Ostrich, Royal, and Sensitive). All like it fairly moist and some protection from the strongest sun.

Good to know I'm on the right track njoasis! I have a clump of ferns already, I'll look for a pink peony to go with the white one. I already have Euonymus fortunei, that's hardy here. I think I lost my bleeding hearts, I'll have to get some more for sure! Can you think of any shrubs for structural interest in winter? Or do hydrangeas have "winter interest"? My azalea looked mighty lonesome. Thanks for the help.

Just to let you know that I am working on the same gardening design challenge in my back yard. There is a large elliptical "island"in the backyard that has a planting of conifers, ginkgo tree, boxwood, and Euonymous. The conifers were already there, I am trying to grow to love them (at least they provide some privacy)--had been neglected by previous owners and were overtaken with English Ivy. As I said, I put in my peonies, ferns, hydrangeas, and bleeding heart. Now, I am considering adding some iris. Iris will slowing spread (but are not invasive, and you can easily transplant them all over the place). My theme is vaguely Asiatic. As such, might also add some chrysanthemum (fall blooming), and Camelia japonica (April-blooming here) and Fatsia japonica. Camelia and Fatsia will not work in your zone but many azaleas are evergreen in colder areas (check for hardiness), also consider holly or boxwood. There are also cold-hardy, non-invasive, clumping bamboos. Happy gardening! (PS. Hydrangea have NO winter interest.)

Almost forgot to mention Hostas--they come in many varieties (all hardy). I'm partial to the blue-green variety myself (some are massive).

Can you think of any shrubs for structural interest in winter? Or do hydrangeas have "winter interest"?

I think hydrangeas have lots of winter interest. Okay not lots, but at least there is something there. And the winter wood is orderly and substantial, unlike so many woody shrubs in winter.

I know they are overplanted and poorly sited (often as a foundation plant) but in a mixed bed, I think they add a lot.

How lucky for you njoasis, to have a few conifers to work with. I don't have room for a background hedge in my deck-side bed, so I'll have to wing it. I did pick up a ligularia and anemone, for late summer into fall flowers. I already have a big blue hosta (Elegans), more hosta will actually be removed to make way for more varied foliage forms. I have a Persicaria 'Painter's Palette' that I'm a little nervous about planting out, it was a gift from a friend, and I don't want to lose it. I also have a bearded iris, but I'm not totally in love with it (it was the PO's) that I could move here.

Two other perennials I'm considering are Solomon's Seal and Great Blue Lobelia. We're diverting the downspout into this bed, so it should stay pretty moist as long as it rains regularly. I don't know that I'll have room for much more, but an evergreen holly is an intriguing idea. Anyone heard of Little Rascal, how does it perform? It's an older cultivar.

Good to know gardenscout that hydrangeas have at least Some winter interest. I noticed that the oak-leaved ones get pretty gnarly looking, I'll have to try one. Maybe next to my spirea.

I bet sweetspire and beautyberry would look pretty good too. Guess anything goes, as long as I can cram it in! Thanks again for getting me unstuck, it's great to hear what works for others.