I've noticed a few different looking Friendly Guild Personal-Bankers, along with all of the other friendly guild staff... How do you change their appearance?
there is a quest in Sunrise Hills to get an item you can use to change the race and appearance of the guild hall employees. The item is the Convoluted Assistant Appearance Augmentator. The quest is A Poem for Arwik.
Both are listed so you can easily look them up.
However be aware that as of a few weeks ago the guild hall employees are not staying as you place them. In other words you can put them down anyway you want but if you try to move them then they face the wall or away from you. If you hail them they will turn to you but will not stay facing that way. They are aware of the bug but have yet to fix it as of June 6, 2021.
Not sure if this will affect changing the appearance also. Personally when I used the augmentator years ago the npc changes did not stay next time I went to hall.