The way to soften the look and feel of a terrace paved with brick or stone is to lay the pavers in sand, then grow plants in the joints. Plants suitable for such a site must be low growing, tolerant of both cold and drought, and invasive enough to keep weeds at bay. The amount of foot traffic also needs to be considered, for not every plant tolerates being stomped on.
Chamomile and creeping thyme are good choices for plants between paving. Besides feathery, lime-green leaves, chamomile offers cheery white flowers all season long. The plants spread by creeping stems and by self-seeding. Especially good thymes for paving are woolly thyme, growing only a couple of inches high, and caraway thyme, whose leaves press right against the ground -- and do smell like caraway. Chamomile releases a pineapple fragrance and the thymes a resinous fragrance when trod upon.
But thyme and chamomile are not the only choices in paving plants. Another is Basket-of-Gold a perennial relative of alyssum, having yellow flowers and woolly, evergreen leaves. The plant rises a half-foot above ground, and its leaves are a few inches long, so Basket-of-Gold is not dainty enough for use between bricks or small stones. Snow-in-Summer also has woolly, evergreen leaves, but they are small. The plant has white flowers and grows a bit lower than does Basket-of-Gold.
Two candidates for paving plants with a lush, mossy look are Pearlwort and Moss Phlox. Pearlwort is dainty, with quarter-inch leaves that rise only a few inches above the ground. Moss Phlox is a familiar plant with tufts of soft, needlelike leaves and bright flowers appearing in spring and sometimes again later in the season.
Get any of the above plants started in paving by sowing seeds or putting in little plugs of seedlings.