These are wonderful and have been using them for a while now.
For the Aquatic form, if you were still looking for ideas, you could use the Nagas for them.
I also have a few ideas for alternatives, but I know they'd probably require a lot of work. If I knew how to do this, I'd probably just try them myself and not bother you
Cat Form: Snake (the ones the Druid of the Fang turn into in the Wailing Caverns)
Travel Form: One of the Raptor mobs, or if possible, one of the Plainstrider mounts of the Blood Elves
Tree of Life Form: One of the 'better' looking Treants (like the ones patrolling the Night Elf towns). I know this would be almost impossible though for the lack of the proper animations and having to somehow shrink the model and such...