Has Philip Pullman ever released or endorsed a complete list of symbols for the alethiometer, along with one or two suggested meanings? I've found this link through Reddit, but I don't know whether it's officially endorsed or simply a fan product.
That list of symbols was published by RandomHouse, the UK publishers of the His Dark Materials trilogy. It can be considered as official as a Disney owned website would be on the Star Wars canon, or Warner Bros on a fact about Superman.
It isn't a fan-made list. Some of the items do match up with the very few meanings that are in the text, and the list of symbols seems to be derived from the cover art of Northern Lights, or at least it is cognate with that artwork.
In the absence of word-of-god, you can consider this list as official as you are going to get.