This question obviously covers a very broad time period; unfortunately I don't know much about the Yijing, but I have a vague understanding that Mao's cultural revolution would likely have destroyed a lot of the scholarship surrounding it, I'm just not sure to what degree. I'm sure I remember reading about a famous pre-20th century Chinese Library burning down, but I might be mistaken.
As well as hints about lost information, I'd be very interested to hear about obscure or esoteric arrangements, uses, and texts surrounding the 64 symbols. I'm aware of two or three arrangements - are there more?
The Zhou Yi is magnificent, but for some reason very little attention is paid to anything else. Is this because of a lack of information, my not knowing where to look, or was the Zhou Yi really pretty much it?
I'm also interested in this.
While you're waiting for a more scholarly reply the following are considered the best examples.
The Richard Wilhelm/Cary F Baynes translation includes all texts, purportedly Confucian commentaries and other commentary fragments available to Wilhelm at the time of translation (1923). This was for many years considered the definitive Western translation.
James Blofeld's alternative translation - Book Of Changes: A New Translation. Is a more cohesive and less fragmented collection than Wilhelm's but also omits much of the additional material. It's this translation that coincided with 60's counter culture interest in Eastern mysticism.
Richard Rutt's Book Of Changes: A Bronze Age Document claims to have material discovered since the Wilhelm/Baynes translation and incorporated this in addition to being a fresh translation it's own right. I don't own this and therefore can't comment on it's quality.
There is also a James Legge translation from the 1870's which while interesting in it's own right bears little resemblance to Blofeld or Wilhelm's version and is generally more 'flowery' as he approached it as he did with the Chinese poetry he translated.
I own the Wilhelm, Blofeld and Legge translations but I don't read Chinese so can't comment on the accuracy of them.