One of the largest collection of ancient mosaics in North America (let's take their word for it) is housed just an hour from me in The Worcester Art Museum in Worcester, Massachussetts--a fact I discovered purely by accident. Two of the most beautiful of these are...

The Drinking Contest of Dionysos and Heracles, laid about A.D. 100 in Antioch.

Hunting Scene, Early 6th Century A.D.
To see more, connect to one of the best mosaic sites on the web: Mosaic Matters.
See also the Italian site
MosaicWorld.
My first mosaic, a copy of a motif from St. Albans.
A copy--in progress on the left and finished to the right--of a Roman Mosaic
in the Burrell Collection (Burley Collection, Al?) in Glasgow.
A teacup
A geometric pattern based on a Roman mosaic.
An allegorical representation of Apolausis, the Goddess of Enjoyment,
inspired by a mosaic from ancient Antioch.
A table top (in marble, smalti, and ceramic tile)