There are some interesting non-humanoid Borg mentioned in the Shatner/Reeves-Stevens novel The Return. It's a shame the TV shows and even movies of the era couldn't afford stuff like that.
There was also a comic where Borg from the future, including assimilated Species 8472, were travelling back through time.
There was also a comic where Borg from the future, including assimilated Species 8472, were travelling back through time.