I'd certainly consider Siberian cypress, Microbiota decussata. An extremely durable and cold hardy groundcover-like conifer, it may get slightly taller than you want and spreads slowly to form a carpet but spread is easily controlled. Takes on reddish and russet hues in winter.

I’d suggest any of the ground cover/creeping juniper species. Most of them will survive in frigid to warm areas. They are very versatile and will do you no wrong

Juniperus horizontalis 'wiltonii' is the female version of blue rug juniper intended for use as ground cover.

Mature size is 3-6" tall and 6 to 8 feet wide but can be contained by proper pruning techniques.

It's a very fine textured, dense, low growing, blue form of J. horizontalis.

It may take on a purplish tone during winter. Mine didn't.

One of my favorites is J procumbens, love that spiky look to it

Is there a dwarf conifer groundcover that grows in an irregular star shape? If I prune a too long arm shorter, then the pruning job would not be as visible (I hope)

Have you looked at the microbiota? Far more interesting and unusual than any juniper and much more easily maintained and pruned. Also will tolerate a lot more shade than junipers.

Yes, I looked at plant, I'm not sure if the winter color is agreeable to me.

If an arborvitae is colored like that, then I'd assume it's dead, am I alone?

But it is not an arborvitae. A variety of conifers - as well as a host of other evergreen plants - will develop those purple reddish tones in response to winter cold. Completely normal and expected.

Taxus canadensis today. Or maybe it did die? ;^))

Hmm.....perhaps I shall be looking for winter gold :-) or no seasonal variation :-)

Generally, in my area, there's enough snow cover that you can't see any 'winter interest' on low growing plants and I don't feel like getting out in the yard anyways. ;-)

I took a hard look at Microbiota decussata this winter and it's still on my wish list (need to find the right spot for it).

Perhaps in milder winter climates it's nice, but going to have to agree, at least here in MN, Microbiota winter color is not that pleasing and people do think they are dead. I use it where shade tolerance is needed, otherwise I prefer Junipers. However, to Bill's point, for most of the winter they get buried so it's mostly the late winter/very early spring does one have to look at them.

That makes me think of gourmet hamburgers that I can't eat, there's no accounting for taste, I guess :-)