The prestige, both cultural and political, enjoyed by Byzantium in the Middles Ages led to a widespread imitation of its arts. Art objects in great number were imported to the West from Constantinople and other Greek centres. Individuals or communities outside the realm of Byzantium, however, were able to secure Byzantine artisans for the execution of monumental mosaics. Abbot Desiderius of the abbey of Montecassino in Italy, for example, called specialists in many crafts from Constantinople to decorate his new basilica (dedicated 1071 ce). Among these were mosaic workers. Of particular importance is the fact that he took care to see that young local artists were trained by the foreigners. This was the pattern that was followed where Byzantine experts were temporarily called in.

The Norman rulers of Sicily, who vied with the Byzantines for control of the Mediterranean, molded their representational arts largely on those of the great Eastern power. The existence, at Palermo, of a central-plan church (Martorana) embellished according to the classical system has already been noted. In other 12th-century churches in Sicily, the Byzantine element is blended with western Mediterranean traits. Cappella Palatina, the palace chapel of the royal residence at Palermo (c. 1143 and later), for example, is a synthesis of a centralized middle Byzantine church and a basilica. The building therefore called for a hybrid program. According to Western custom, the mosaics of the basilical parts depict narrative cycles: scenes from the Old Testament and from the lives of Saints Peter and Paul. In the centralized part of the church most of the features belonging to the classical system are at hand. There is a bust of the Pantokrator in the dome, surrounded by angels, but as a concession to the longitudinal disposition of the church, the Pantokrator reappears in the apse.

Martorana and Cappella Palatina were decorated by Byzantine artists, a fact borne out by the brilliant technique, the purity of the Comnenian style, and the adherence to Eastern iconographical prototypes. Two large basilicas are among the highpoints of this Sicilo-Byzantine flowering: the cathedral of Cefalù (c. 1148) and the church of Monreale, the last of the mosaic churches of Sicily (c. 1180–90). Demus has pointed out the extraordinary homogeneity of style and technique in the Monreale mosaics, which constitute the largest decoration of this kind in Italy. He has also shown that the Monreale mosaics are not executed in the refined and softly curved style that dominates in Cappella Palatina and at Cefalù. Monreale is infused with a more agitated and expressive style which, however, has nothing local or provincial about it. It was the late Comnenian style of Constantinople which had then reached Sicily—a testimony to the unbroken artistic contact that existed at this time between the Norman court and Byzantium.

Venice, for a long time commercially active in the eastern Mediterranean, enjoyed similar but more long-lasting artistic connections with Constantinople. A church that in the 11th century must have looked exotic as well as old-fashioned, St. Mark’s was copied after the venerable Church of the Holy Apostles at Constantinople, an early Byzantine, many-domed type that had long since gone out of favour.

The mosaic work undertaken at St. Mark’s lasted more than two centuries, from the end of the 11th to the middle of the 14th century. The many and marked stylistic disparities can be ascribed in part to the changes that affected Byzantine art during this period; but they may even have been caused by the freer, Western organization of the Venetian workshop, which allowed artists to develop and cultivate their own personal styles. Among the variety of styles, the Byzantine element is dominant, but it is modified by local tendencies and particularly by strong Romanesque impulses.

The workshops established in Sicily and Venice were active in the neighbouring areas. Mosaics in the cathedral at Salerno (c. 1190) and in the monastery at Grottaferrata near Rome (c. 1200) are regarded as products of the Sicilo-Byzantine school. The apse decoration of the cathedral at Ravenna (early 12th century), of which fragments survive, seems to have been the work of mosaicists from Venice and, in Florence, Venetian artists decorated the dome of the Baptistery (1225–1330). The much later mosaics on the facade of the cathedral at Prague (14th century) are also Venetian.

In the early Middle Ages, Rome had been able to maintain and defend a mosaic tradition of its own despite the Byzantine hegemony in the arts. At a period when Iconoclasm had loosened the ties between Byzantium and the West, at the end of the 8th century and the beginning of the 9th, the influence of the Roman school extended even into the Carolingian Empire. The apse mosaic of Germigny-des-Prés, France (between 799 and 818), is a product of this influence. In Rome, the pontificate of Paschal I (817–824) left three monumental decorations which constitute the best sources concerning the artistic intentions of this time: the sanctuary mosaics of the churches of Santa Cecilia in Trastevere, Santa Maria in Domnica, and Santa Prassede (attached to the latter is the domed chapel of San Zeno, also fully decorated with mosaics). The iconographic schemes of these 9th-century churches largely reflect local 5th- and 6th-century church decorations. Also remarkable is the return of many of the technical idiosyncrasies of the early Christian period, including the employment of large tesserae for faces and dress and the use of glass for all parts of the composition. The setting of the tesserae is, however, loose and disorganized; and their varying shapes suggest that they are reused cubes taken from older monuments. Stylistically, the mosaics of the Paschal period, with their extreme two-dimensionality, are related to Byzantine mosaics of the 9th century (the cupola of Hagia Sophia, Thessaloníki), but technically the differences could not be greater.

Little is known of the art in 10th and 11th century Rome. But from the 12th century, a group of works testify to continued inbreeding. The apse decoration of San Clemente (the 1st half of the 12th century), for example, contains a scroll pattern (rinceaux) reproduced from a 4th-century decoration in a technique that in many respects resembles that of the Paschal mosaics. This isolation, or resistance to foreign influence, seems to have been broken in the 13th century. In 1218, Pope Honorius III asked the doge to send craftsmen for the decoration of San Paolo Fuori le Mura (1218). Several important mosaics from the later part of the same century reflect the trends current at that time in Byzantine and Italo-Byzantine mosaics. The mosaics by Jacopo Torriti in the apse of the basilica of Santa Maria Maggiore (c. 1290–1305) are among the finest of these. They show a mingling of Western medieval and Early Christian iconographical features, such as a scene of the crowning of the Virgin surrounded by the scrolls of a fleshy, classicizing rinceaux; but the lower zone with scenes pertaining to Mary reflects Byzantine influence, an influence also seen in the technique and colour scheme of the mosaics.

Floor mosaics had a renaissance in the West that was unmatched in the Eastern Empire. In the early Middle Ages the Byzantines developed their particular form of floor covering consisting of a geometrical mosaic made up of pieces of marble of various sizes and shapes (opus sectile) usually with some tessera work added for special coloristic touches. This art, called Cosmati work, spread to the West, in which, however, there was also a revival of the tesselated pavement. This pavement, which had survived the Dark Ages in a very primitive form, reemerged in Italy in the 11th century in greater splendour. There are impressive remains of such floors in many of the larger Italian churches. The fashion spread to other parts of Italy and even to France and Germany. In France, where large floors were produced in quantity in the 12th century, fragments of outstanding quality are found—for example, in Saint-Nicolas at Reims (last half of 12th century). Cologne seems to have been a leading centre for this art in Germany. The style of the floors is usually one of simple outlines and light colours, though in some cases figures and ornaments appear against dark ground. The programs draw their inspiration from many sources, such as textiles, early floor mosaics, and the sculptural ornamentation of churches. An exceptionally well-preserved example is found in Otranto in the Italian province of Apulia, now Puglia (1163–66), where vast floors depict scenes from the Old Testament and mythology (the ascension of Alexander), representations of the Zodiac, and of the labours of the month. A profusion of monsters and fantastic animals fills out the picture of a decoration cast in the Romanesque iconographic tradition.