I found some infos. Not 100% what we need but close enough.
1) I found the lord of Thessalonike at 1081. His name was Nicephoros Melissinos and was a cousin to emperor Alexius Comnenos. The book also states that his dynasty ruled for many years.
2) I found the description of a banner that had Thessalonike at 12th and 13th century. It states: It is a gate with a triangle gable on its top. Right and left are two towers with battlements. In the botom of the banner it is written +CIVITAS THESSALONIKI-CARUM
When the latins came, they kept the banner and add at the other side Boniface to ride a horse.
When the latins were gone the banner changes a little. It has the previous gate to be kept by St. Demetrios and emperor Manuel Paleologo.
Just to note the gate represents the city of Thessalonike.
It states nothing about the backround of the banner but I would suggest gold (as it is the backround in the mosaics of the byzantine churches), or dark-lush red aka porphyra (royal colour of the macedonian dynasty, though the Ducas are a different dynasty, i find very possible to have such a color), or a rich blue (a typical royal color). From these three backround colors I would prefer the red and the gold and from the last two probably the gold.
The source is a book from the University of Ionnina and tomorrow I will have a photocopy of it. To verify what I am saying I can scan these parts and give it to you. The only difficult part is that is written in greek. So someone who knows greek can verify what i am saying.
Demetrios always had a notion that you know greek (probably is the name

). (Btw St. Demetrios also is the Saint protector of Thessalonike)
Tomorrow I 'll post the scans.
Is anything else that is needed to be done by me?
Thanks for the patiance
PS. In a previous post I said that Thessalonike was one of the “themata” Here is a link that back it up:
http://www.fhw.gr/chronos/09/en/p/610/main/p4a.html
Also there an encyclopaedia link that states that Thessaloniki was the second after Constantinopole.
http://reference.allrefer.com/encyclopedia/T/Thesslnk-history.html