Answer: Low, spreading evergreen conifers are good choices in groundcover, especially where you want to provide some winter interest but leave the spotlight to flowering bulbs, perennials and annuals in other seasons. Groundcover conifers will make a quite background to these showier plants. They can also be a good choice for covering a slope.
Juniperus horizontalis ‘Wiltonii’ (shown; Zones 3–9) and J. h. ‘Bar Harbor (Zones 3–9) both stay quite low and send out long branches. Both are a blue-gray color year-round.
Microbiota decussata (Zones 3–7) looks similar to a low juniper but adds the bonus of foliage that changes color through the year. In summer, it is pale green; in iwnter it turns a rich bronze. Juniperus communis var. depressa (Zones 2–7) is a mat-former that looks brownish green in summer and bronze in winter. Such plants are nice because they fade into the background during the warmer months and shine in the cold, just when you need them. Both look great near blue spruce in winter.