I had considered flowers like pansies. They're low growing and come in a variety of colors that would compliment the red lace leaf maple. But then the blooms would eventually fade even though pansies thrive in cool weather.
Another option, I had considered was to go with a type of creeping and trailing conifer. The needles would make the eventual naked tree attractive in the winter; kinda like being wrapped with a furred collar. I haven't found what I'm looking for. At the same time, the limited colors of the needles do not excite me.
Then I learned about sedums. They are succulents and like many succulents, they can survive winters. They also produce pretty little flowers that are either bright yellow or pink or bright red, which compliments the dark foliage of the Tamukeyama. Some sedums are low growers. They are also drought tolerant and do not require a whole lot of maintenance. I also like how sedums looked when mixed grown with a limited variety of sedums. I became excited about the potential addition of sedums in the garden.
The next day while walking around the greenmarket in Union Square, I noticed one of the vendors was selling sedums and of many kinds including the "angelina" and "dragon's blood". There were at least 6 different kinds of sedums. I initially picked out six but returned half because I noticed they were infected with aphids! I kept Angelina, Blue Spruce, and Stoloniferum Green. I'm hoping to add Dragon's Blood, or Red Carpet (sedum spurium), or a John Creech.