Red-twigged dogwood would show well against the white siding. The brick is too far down to be of any consequence, as I see it. There is also a dogwood with yellowish green stems that you might prefer. In either case, it's good to prune out a few of the older stems every year, as the younger ones have better colour.

You might also consider a weeping pea shrub. They are nice and hardy, and wouldn't outgrow the space.

The globe cedars could stay, you could add dogwoods or something similar and the contrast would make both look more interesting. Of course, then you might have to move flowers to a bed in front of the walk... How distressing. ;o)

Another possibility would be a prostrate yellow evergreen to provide a shape, colour and texture contrast to the cedars. Or all of the above...

Does anyone have a weeping pea in full shade? It's beautiful, but the web sites I found it on says full sun to part shade. Same thing about the dogwood, will it grow in full shade? I have always wondered how the thuja stayed alive, because to be honest, 1 hr of filtered sunlight is the max that spot gets.

I have a variegated red twig dogwood on the north side of my house in pretty much full shade. It really brightens up the dark corner beside my front porch. It doesn't bloom much but the flowers aren't that exciting anyway. I have white siding also and the red stems stand out nicely in the winter time.

For winter interest in green, you might consider kerria japonica, which has several cultivars. It has green stems which stay green all winter. It has yellow chrysanthemum shaped flowers about an inch across that start (in zone 5) in May with a bush-covering flush, followed by periodic reblooming. It grows fine for me in shade, and for my neighbor also in full sun. Left to its own devices, it grows to 3-4 feet in shade. It accepts pruning well, and since I have it in a windy location, the very tips will die back a little.

One caution is that it spreads by stolons that run just a couple of inches below the soil surface, so be prepared to contain it or share it with friends and relations!

I looked up the kerria japonica. It's beautiful. I am going to try to find it for that spot. Thanks so much!

Kerria japonic and red twig dogwood are both wonderful plants! I prefer K. j. to the more mundane forsythia and it blooms nearly as early.
Another option would be oakleaf hydrangeas. Beautiful large oak leaves, large panicles of white flowers in summer, and lovely, exfoliating bark in winter.
Shady garden with oakleaf hydrangea blooming:

Ooo, pretty! I wish I had a shady corner to do that with!

"Winterberry" shrub is nice for winter interest. Here's a few links that show you it's winter attraction:

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dainaadele: I don't know if this helps, but I have my grafted weeping pea shrub tree on the SE corner of my house, where it is shaded by some mature city maples in the morning and by my neighbor's house in the late afternoon. It only gets some sun at "high noon". It is doing fine. I do not know if it could go fully shaded though. Right now mine is flowering yellow flowers which will soon form lovley dark spiral pods. I think this plant would do well in the shade but maybe you would not get the abundance of flowers??