Pansies are very pretty flowers to plant in fall and they do well thru early spring.

Sedum Autumn Joy will keep seed heads over most of the winter and there are other sedums that will put out nice rosettes late in the fall and stay green for the cold weather. Here in zone 7 (Richmond, VA) Creeping Jenny makes a good groundcover that stays nice over winter, but it can be invasive so be careful where you plant it. Ajuga lasts over winter, too. Helleborus orientalis (Lenten Rose) is pretty in winter and has the added benefit of blooming while most everything else is still sleeping. If you have a shady area, there are some evergreen ferns that look nice in winter, too. Check with a local nursery or look online for evergreen varieties. This is just a short list. There are many more. Ask at the nursery and see what they recommend.

I have Sacaton grass, which gets to be about 7 or 8 feet tall and 5 feet in diameter. Also, thread grass, Purple fountain grass both will probably look good.
Among perennials with winter interest is ecynacia (sp).
Evergreens are an obvious choice.
What thrives in your area, however, might well be challenged by our climate
Norm

Miscanthus is beautiful in the winter-it not only turns to a pretty wheat color, the blades curl up, looks really nice.
Well now that I think of it, it was called 'gracillimus' I think, sorry for the bad spelling. One of my roses, William Baffin, is really pretty in the winter, red stems. Also any of the roses that produce hips are pretty in the winter.
And any structural things like obelisks, etc., look really pretty w/the snow.

I like my Sedum 'Autumn Joy' when they wear a snow cap. Hydrangea 'Annabelle' seedheads are attractive too. I have seen pictures of Stippa tenuissima that are so pretty in winter. Yuccas are pretty too.

Check out the book "Year-Round Garden" by Adrian Bloom - the edition that comprised two parts that had originally been published separately as "Winter Garden Glory" and "Summer Garden Glory"

The listing of plants are a bit outdated since there are many more plants available now, but the pictures are gorgeous and I think the book is a wonderful resource for winter gardening.

I have these grasses:
Calamagrostis x acutiflora "Karl Foerster" Feather reed grass
Molinia arundinacea "Skyracer" ornamental grass
Panicum "Shenandoah" switchgrass ornamental grass
Pennisetum alopecuroides "Hameln" ornamental Fountain grass

All have winter beauty. I especially like the Karl Foerster planted in a tight zigzag row. It holds long golden, gently waving seed heads and can reach 5 feet tall. I also like my row of fountain grass, which is planted in my garden bed. Both are in view of my windows and look great in new snow. The others I have planted alone as accents and tend to fall over midwinter. This may be because they are solitary accent plants and not supporting each other in rows.

I wish I had checked on which grasses are sterile. Now I wonder if some are seeding in my garden beds.