The lock on Haru’s mother’s strongbox is shaped like an upside down bat:
A picture of a bat (fu 蝠) can be a visual pun for “good fortune” or happiness (fu 福) because both characters are pronounced fu. Often the bat is shown flying upside down because the character (dao 倒) for “upside-down” and the character (dao 到) meaning “to have arrived” are both pronounced dao.
Source: one
Omashu: Bumi
Repost: Wherein Jin finds new sources while doing research for other stuff:
Bumi’s character seems to be based on Lü Bu
A General from The Three Kingdom era.
Throughout Romance of the Three Kingdoms, Lü Bu has been depicted as a ruthless and impulsive warrior who has no sense of loyalty and sympathy. It portrayed Lü Bu as an invincible warrior but an incapable leader who is further marred by character flaws.
Lü Bu was eventually defeated and captured by Cao Cao at the Battle of Xiapi. At Liu Bei’s suggestion, Cao Cao had Lü Bu hanged.
The feathers on Bumi’s hat/crown are also present in Beijing or Cantonese opera.As the quote says: In Beijing Opera the feathers are attached General’s helmets for the purpose of expressing and underlining emotion.
Bumi’s crown: reference (#6) 
i called 双雉盔 and worn by the Three Kingdom hero Lu Bu in video games, movies and manga. I am not sure how valid a source that is XD and how much of that and the Beijing Opera costumes is chicken and egg.
The quote is from: Beijing Opera Costumes by Alexandra B. Bonds p44
Hairstyles
Neither Fire Nation topknots, nor the Earth Kingdom ones are Japanese/Samurai. They are Three Kingdom inspired.
Let me first note that it is a pain to find any real references for guys’ hairstyles through the ages. Girls’? SURE. Guys’ not so much. It also does not help that the time period (Three Kingdoms and Tang Dynasty) that the majority of the hairstyles are taken from are extremely popular. Any search will find a gazillion TV shows, mangas and movies before it will find anything that even remotely resembles a real source.
After several days and countless hours I’ve given up. You are getting movie screenshots. Feel free to google/baidu Tang Dynasty TV show or Three Kingdoms for more pictures.
Omashu: Soldiers
And with Omashu we’re back on track with things Jin knows about :D
The references in Omashu are plenty, so I’ve decided to split them up into several topic posts.
The soldiers we see in Omashu are wearing a combination of Jin , Liao and Song Dynasty armor i.e. see the armor girdle. These dynasties share roughly the same time period of 900-1200 CE.
The studs on their wrist guards look more like the later Qing Dynasty to me. The Qing influence is more pronounced in Ba Sing Se and will be discussed then.
When Aang goes into Avatar State at the Southern Air Temple, we see a sequence of temples light up in response.
The one in the Earth Kingdom (first picture) resembles the Temple of Heaven in Beijing, in style, architecture and coloration. This is not surprising, since A:TLA seems to go for a Manchu parallel for the Earth Kingdom, which will be particularly obvious once we compare Ba Sing Se and Beijing.
The temple that lights up in the Fire Nation is pagoda style:
A pagoda is the general term in the English language for a tiered tower with multiple eaves common in Nepal, India, China, Japan, Korea, Vietnam and other parts of Asia. Some pagodas are used as Taoist houses of worship. Most pagodas were built to have a religious function, most commonly Buddhist.
It also features the traditional Chinese curved roofs (to ward off ghosts), which place it within the Buddhist believe system.
The recognizable curved roofs of oriental architecture reflect a Buddhist belief that ghosts move in straight lines (and hence will bounce off a tapered roof), as does the presence of a ‘ghost wall’ just inside the entrance of some homes.
