Quite some time ago, The Queensland Wargamer, the journal of the Queensland University Games Society, published a series of role-playing articles titled 'Roleplaying In Asian Settings'. Three of those articles are of particular interest for any Celestial Empire campaign, and are thus linked here:
㊁ CHINESE JUSTICE
All of Robert van Gulik's Judge Dee novels end with a Postscript that contains a lot of information as to how Chinese justice was carried out in Imperial China.
㊂ CHINESE ALCHEMY
Chinese Alchemy is a complex subject, and describing it in gaming terms would probably warrant a whole game supplement onto itself. The following is a brief introduction to Daoist Alchemy:
㊃ CHINESE SEAPOWER
There used to be an interesting article on Míng ships and fleets, but it is not on-line any longer. I have provided a link to a snapshot from archive.org: