Hello there!
I've been working this afternoon in some banners for my SS Crown of Aragon and I decided to make a set of banners for the former Kingdom of Aragon. As you said that banners change when a faction "evolves" into another, then I decided to post my banners here for if you can find some use for them.
The first one is for the Kingdom of Aragon:

I'm afraid the capture has not the resolution I wanted.
The first banner is the Cross of Íñigo Arista, originally the signum of king Remiro I, but sightly modifyed. It should be white instead of yellow, but as that's what you're using as faction symbol, and besides it's cooler this way than the traditional way...
The second one is the Cross of Alcoraz, a Saint George Cross with four moorish heads, remembering the conquest of Huesca in 1096 led by king Pedro I.
The third one is a design that I invented, but it's based on this one:
I'm referring to the left side of the shield. This is the true signum of king Remiro I. I just centered the cross and triplicate it.
The last two are the Cross of Rada and the Tree of Sobrarbe. The Cross of Rada is the heraldic symbol of the county of Rada, in the Pyrenees. The other represents one of the initial counties of Aragon, Sobrarbe, which was believed to be the last refuge of Christians in Hispania after the Islamic conquest.
Then, I've made the banners of thwe Crown of Aragon:

The first one I've explained before. The second one goes for Barcelona. The Saint George quartered with the Four Bloody Bars are the symbol of Barcelona.
The third one is the Senyera Coronada, the Crowned Ensign. Today's the flag of Valencia, but some believe that was created by king Jaume the Conqueror and used as personal ensign. I don't know if that's true or not, but I get the chance to use such a beautiful banner.
The fourth is the plain Saint George Cross, for it was the banner of the Military Arm (the nobles) in the Crown of Aragon. Besides, Saint George was the patron saint of Aragon and Catalonia.
Finally, the Senyera, or Royal Ensign of Aragon (Senyal Reial d'Aragó), four bloody bars on a golden field. The legen tells that it was Count Guifré the Hairy who, while dying after the failed conquest of Lleida at the year 897 AD, asked to the Frankish King Charles the Bold for an ensign for him and his family. Then, Charles put his hand in Guifré's mortal wound and drew four lines of blood with his fingers upon Guifré's golden shield.
I've done two more banners, in case you need them:
This is the ensign of the city of Zaragoza. It was not yet under Aragonese control in 1100, but Alfonso the Battler would conquer it in 1118 and make it his capital city.
And this last one, for the Crown of Aragon:
That's the heraldic ensign of the powerful Montcada dynasty. It was possibly the most powerful family in high Medieval years, between 1180 and 1300, and achieved the title of Stewart of the Kingdom in heritance. After the dead of the two most prominent members of the family, the dynasty began to decay to make way to another family: the Cardona dynasty, which would become the most powerful family in the Crown of Aragon unit XVIth Century, when the last Duke of Cardona, Grande de España, died with no male heirs and his daughter married the Duke of Sogorb, a Castillian, who later would merge his title to that of the Duke of Medinaceli, a great Castillian noble bloodline which still exists today.
That's all. I hope it can help you somehow.
Take care!
PS: Sorry, I don't know how to make spoilers...