Lizard, Scorpion, Tiger, Bear
You already have tinkerbell(titania) and a whole host of other human characteristics. Some story line that goes on about how the human enhanced were being figured out and starting to have difficulties so the option to use animal traits in the hopes of creating feral warriors of the tenno... but then things(lore) happened and the frames were never put into service.
Oh and Im not in it for the contest. Just throwing out idea starters. Would love to have a scorpion Frame with a tail that is used with 4th ability.