I had been interested in doing a Byzantine Army since the recent new Gripping Beast and Crusader figures started to come out. When I bought the Warhammer Ancient Battles Byzantium: Beyond the Golden Gate supplement (very much the best of these, in my opinion) I realised that it was all more complicated than I thought and I would need to decide which period Byzantine Army would be best, as the troops look very different in different periods.
I was also inspired by several novels I have read recently. The first are Tom Harper's two books (The Mosaic of Shadows and the Knights of the Cross) set around the time of the First Crusade (around 1095) and featuring a "detective" from Constantinople and his Varangian associates. There is not much military action in the first one (although it does give a good feeling for Constantinople) but the second features the siege of Antioch and while more appropriate to building a First Crusades Army does have the Varagnians in action. The third in the trilogy, Siege of Heaven, is due out in February 2006 (not long to wait!) and will focus on the siege of Jerusalem.
The second book is Tim Severin's recently published conclusion to his Viking Trilogy (Viking: King's Man) which features a section set during the Byzantine campaign against the Saracens in Sicily (around 1040 I reckon). I have been vacillating over what sort of Byzantine army I should build for some time. In many ways a Justinian army would suit me better as I am planning to build a Sassanid army to take on my A&A 3rd Centry Romans, and this would provide an extra opponent. The only really suitable figures, however, are Old Glory, which I don't like (due to the variable quality and requirement to buy large bags) and Chiltern Miniatures (ex-Whitecross) figures. These are better but a little on the small side and lacking in variety of poses.
The passage in Tim Severin's book where regular Byzantine troops, including cataphracts and menaulatoi combine with Norman mounted mercenaries and Varangians to take on the Saracens at Syracuse has decided me, however. I now plan to prduce a Thematic army for the first half of the 11th century.