Plenty of decent suggestions!
My old garden was zone 5b and had more shade than sun. I did not have the added grief of Black walnuts but I had deer, lots and lots of deer.
The recommendations really will depend on how much sun your shaded areas get. I had small zones within the beds which got as much as 4 or 5 hours total sun and some that got only dappled or a couple of hours of early morning sun and used different plants for each piece.
Hydrangeas are known for having greater sensitivity to juglone. If you can plant them far enough away you will want to be aware that not all are good candidates for frosty/freezing no snow covering winters. Some are borderline for zone 5 (especially if it is 5a or verging on 4) and need additional mulch protection in winter. Oak leaf hydrangea tend to like more sun than the others so it will need to be in the sunniest possible part of the garden. Midway down the following is a good summary of general survival abilities of the different hydrangeas: Hydrangeas Plus
Black Walnuts tend to turn a few plants into yellowed sickly looking things pretty quickly so they've gotten bad reputations. People have lost lilies and peonies to their walnuts although some peony varieties seem more resistant. On a more positive note there are actually quite a few plants that can withstand the juglone that the walnuts release in the root zone. The following should do well in part sun to part and full shade, and in zone 5 from my own experience: tradescantia (aka spiderwort) Campanula latifolia (Giant Bellflower), Heuchera (Coral bells), Astilbe, Hosta (all kinds), primroses, pulmonaria (lungwort) and in the sunniest possible spots even physostegia (aka obedient plant or false dragonhead)) garden phlox and perennial geraniums (aka cranesbill or Geranium sanguineum) and daylilies will work. Several ferns will also do well in those conditions.