Having flowers on your stoop is necessary all year round, and in my opinion, ornamental cabbage and kale make excellent choices. There are many different kinds, and they pair well with evergreen grasses and winter pansies. Ivy adds a nice touch trailing over the edge.
Pictured here is an ornamental cabbage, variegated ivy 'Glacier', winter pansies, and an ornamental grass Acornus* 'Ogon'.
*Acorus is a neutral grass. Evergreen or neutral grasses are usually plants that look like grasses but aren't actually classified as grasses, they are generally called grass-like plants. Divide evergreen or neutral grasses and grass-like plants in spring only. Evergreen grasses don't ever go dormant. Dividing plants wounds them to some degree. For evergreen grasses this wounding will really affect their ability to live through the winter.
Pictured here is an ornamental purple kale, Acornus 'Ogon' grass, pansies, and ivy. I threw a little Swiss Chard in this one hoping it makes it through some of the winter.