15th Century Byzantine Flags?

[Condottiere]

The star and crescent...

Seriously, check out Byzantine Naval Forces 1261–1461: The Roman Empire's Last Marines.

IIRC, the double-headed eagle and the B and B flag was used by the Palaiologoi and not prior dynasties, though I've read of a 10th Century origin, so Macedonians too? The double-headed eagle is a traditional Anatolian image and was used by the Hittites and Seljuks. According to Dawson, since the late 7th/8th Century, units were ad hoc, so relied on simple geometric designs - like 17th Century regiments? Don't know why there's nothing for tagmatic units...

This is a decent introduction: Standards and insignia of Byzantium, Byzantion LXXI (2001).

[Atheling]

I've downloaded the Pdf so thanks again Condotteire 

[Condottiere]

Some heraldic references:

On the Wings of the Double-Headed Eagle: Spolia In Re and Appropriation in Medieval Anatolia and Beyond by Suna Cagaptay

Byzantium between East and West and the Origins of Heraldry by Robert Ousterhout

Imperial Usage of Zoomorphic Motifs on Textiles The two-headed Eagle and the Lion in Circles and Between Crosses in the Late Byzantine Period by Bojan Popović