During character creation, if you choose to be the child of an impoverished noble, you will be given the option to carry a banner from the start of the game - otherwise, you don't receive a banner until you have become a vassal or monarch.
Your own banner will also be planted in the ground during battles at your side of the battlefield right next to your inventory chest. This makes finding your chest if you need to swap equipment or reload arrows much easier.
Since most banners are already in use, if you choose one that is, its original owner will receive a red and white diagonal checkered banner instead, which is not available to player. There are a few banners that are not already in use, however. If you use the cheatmenu to change your banner again, your old design does not return to its former owner, rather there will be multiple lords with the same checkered banner.
Warband added a new faction with new vassals, and so expanded the number of options to choose from. The following displays all banners as seen in Warband, altogether there are 128 flags to choose from.
With Fire & SwordEdit
In keeping with the historical nature of With Fire & Sword, many of the banners are based on flags and standards from history, such as the flag of Sweden, the banner bearing the knight and eagle of the Polish-Lithuanian Commonwealth, and the rifleman icon of the Cossack Hetmanate. Unlike in Warband, players have no option of starting the game as a noble, so they cannot carry a banner until becoming the vassal of a nation.
All the banners available in the Viking Conquest DLC. A total of 177 banners.