I'd recommend giving probably round shields to some or all of the:
Peltastae
Acritae
Toxotae
Mourtati
Reasoning:
1) From Ian Heath's Armies and Enemies of the Crusades 1090 to 1290: http://d.imagehost.org/0668/Byzantines.jpg
2) Osprey's MAA 287 Byzantine Armies 1118-1461
- Page 18, Illustration from Romance of Alexander the Great (hard to place the date, they say the archers have shields commended in the 10th century. The Heavy Archers have circular shields on their arms or backs
- The first illustration by the Osprey authors has an infantryman, armed with sword and a very thin spear, and a leather jerkin. The commentary mentions "other light infantry carried only a bow and shield"
From Armies and Armor of the Crusading Era (Al Mansur I think has access to it, so he can verify it for me)
1) #116 - depiction of "Goliath" in a 12th century Byzantine manuscript. HAs Goliath armed like a byzantine skirmisher, with javelin, straight broadsword, large round shield, and what seems to be a chapel de fer(kettle hat).
2) There is another depiction of a very well armored archer (With mail shirt, mail chausses) but without a shield, but there aren't many other depictions of ranged troops in it.
Lastly it's because without shields, archers and javelineers are left exceedingly vulnerable to the always shield equipped Latin Archers/Crossbowmen (at least the higher end troops). Might also recommend giving spathae swords (Saw one ingame) or other ones to at least the elite archers/skirmishers.
Also might suggest giving the itm_woolen_cap to the starting byzantine city/village levies, maybe also the first level Peltasts and Toxotaes (since that Phyrgian style cap seems popular for Anatolian troops).