For the year around interest you may plant rhododendron PJM (lavender) or its little bid smaller cousin 'Olga Mezitt'(pink). Both should be hardy for you and bloom before dicentra. Another possible shrub to consider is Kerria japonica. It will be in prime (in considerable shade) just when dicentra only start blooming.
For the summer only interest, large ferns like ostrich or cinnamon ferns behind dicentra will create whole summer interest. Location should be moist, though.
Kerria in prime, ferns only sprouting, dicentra beginning to bloom. First week of May in my zone.

Two weeks later. Kerria is almost done, dicentra in prime and ferns need another week or two to overpower dicentra.

Thanks for the suggestions and the pics of your beautiful woodland garden, EGO45! Love how radiant and cheerful that kerria looks. We have a kerria elsewhere in the yard which I've considered moving into this shady area, as I'd heard they bloom even in quite heavy shade. I wasn't sure how the golden kerria blossoms might look with the dicentra, but it works in your garden, perhaps because of the surrounding green context. Azaleas haven't done real well for us--soil is quite alkaline. After I wrote that post, I thought about maybe putting a shadbush there--could prune it so that it just sort of hovers over the dicentra and doesn't grow into them. Hmmm...will keep thinking about moving the kerria.

Another thought would be spicebush. Lindera benzoin. My berries stay on all winter and although it's ca. 100 feet from the house shows up nicely.

Found third picture of the same bed when ferns become a main feature and dicentra just an accent:

Later on (when dicentra flowers will be gone), ligularia przewalskii (yellow flowers) and fallopia japonica 'Variegata' (bright, almost white leaves) will brighten up the space. After that Kirengeshoma will bloom and become a main attraction.
I'm thinking of adding even more later blooming simicifuga ramosa 'Atropurpurea' there, but bed is pretty crowded already and considering ostrich fern's spreading nature it might be problematic to find a space.