Before buying a banner slot I activated a regular clan banner und the "use clan's banner" in the warband character menu. It showed correct on the homepage, but ingame the banner was kind of random. It switched between rounds and maps, didn't notice any logic behind.
Don't know if it's related to the known banner bug, which is still unsolved, ingame banner is from the former owner of banner slot.
Edit: Now the ingame banner is correct
