Try planting up some containers with year round plants that are shade tolerant - a variety of small shrubs, hellebores, heucheras, ferns and some grasses will all grow quite happily in a low light situation and are evergreen. You could also select something with some variegation to add brightness - Euonymus fortunei cultivars work well in containers, are very shade tolerant and come in both white and gold variegated forms. You could include some wintergreen, Gaultheria procumbens - its foliage will turn a deep maroon in cold weather and it also offers big red berries. Add seasonal color with winter pansies or later, primulas. FWIW, except in the coldest weather, I've grown florist's cyclamen in outdoor containers all winter - they just need to be out of the worst of the weather as they don't hold up well in lots of rain.

Some of the smaller Campanulas are very shade tolerant, too. Various shades of blue, and white.

Box as a topiary to give height and 'a statement' - and box is quite comfortable with winter gloom.

If you get good indirect light and you can provide frost shelter - you could consider both Veltheimia and Clivia in containers. Clivia flowers over winter - orange or yellow - and not as harsh as that might sound. Veltheimia is more a dusky pink.

Some of the low-light bromelliads might suit, too - if you have a suitable microclimate.

I think the key word here is winter interest - neither the clivia nor the bromeliads will successfully winter over outdoors in a Pacific Northwest zone 8 climate. And campanula, which will bloom very well in a low light situation, doesn't bloom here in winter.