In my opinion, since there are no shamans and the druid is the only one linked to nature, we can get more out of it. For example, we could assimilate each form to an element.
Dps Mele: Ice werewolf, with slow abilities and some stum
Dps ranger: An electric bird ( phoenix ?) depending on haste, mastery and critical you could focus on area or unitarget damage
Tank: Rock boar, harden abilities for magic or physical damage and crowd control, stums, ccs, etc
Heal: Mushroom, water elemental or raccoon form (i find it funny). Plant and water based healing abilities, some cc
travel: Rat, which would allow us to climb small walls or sneak through small places for specific class missions, or to be a able to flee from and ambush. we would be slower then using mount.
Travel by sea: Octopus? I think it would be funny, pretty and good novelty
I dont know about you bit I´m tired of the typical forms of bear,owl,cat, etc