If you go back to the profile page and enter your area and zone this would be easier to answer. Without knowing where you are located; this is a vague question.

Oh, yes, that would be helpful! I'm in zone 5.

GreenQueen - great name!

I'm bumping this up not because I have an answer but am interested for a friend of mine in a cold zone. A total guess would be that the exposure to the elements of a container that size would allow complete freezing of the contents.

I'm not sure what you mean by "looking good all winter". If you are looking for plants that have parts above ground that remain interesting after having been killed by frost, a few net searches will turn up plenty of plants that you could try. However, your request is difficult if you are looking for material (such as evergreens) that will remain viable through a zone 5 winter, unprotected and still look good. As a guideline, I usually advise that plant material in containers (for zone 5) that are in contact with the soil or that gain some warmth from an extraneous source, like a heated dwelling, should be hardy to zone 4, and those plants with no protection, like yours (solar gain doesn't count as an extraneous source of heat in your case because of the small volume of soil and the fact that there is little in the way of a "sink" in which to "save" heat from the sun), should be hardy to zone 3 if you wish to count on their survival. This is not to say that some zone 4 or even 5 plants can't survive your conditions, but there are few plants out there that can survive actual root temperatures in single digits. Even when it is extremely cold and frost penetrates the ground to 2 feet or deeper, it is unusual for actual soil temperatures at 6 inch depths, even in open fields, to drop much below 25* F. I'm skeptical that any of the plants you listed will overwinter w/o protection.

Remember that whatever plant material you choose, you'll need to water fairly often when temperatures go above freezing, especially if the planters are also constructed of cedar. They will dry quickly.

I'm not sure if I answered your question or not, as it is unclear what kind of winter interest you're looking for.

Al