Hi Nadja,
This is expected behavior. Branding is a per-appliance setting, similar to session recording mounts. As such, you will need to update each appliance manually. The reason this option is per appliance is because many people choose to use this as a way of identifying which node you land on. For example, many customers will put 001, 002 or A, B in the image so they know which appliance they are actually on.
Let me know if you have any follow-up questions about this.
Regards,
Christian Lutz
Sr Support Engineer
Broadcom (CA) - ESD Support