I have been somewhat hesitant in posting in this thread simply because you are almost asking for a game design to be provided to you.
What kind of game will be my game?
A simple suggestion for a Tower defense game.
Embattled human's have retreated into highly fortified bunkers, redoubts, castles and whatever stronghold they can find. You with your army of animals must break down these fortresses and make those Those Damn Dirty Humans pay! This idea operates on premise that you use humour throughout the game.
From the human perspective: (Passive Defense) Various traps are laid around the defensive compound: These traps could range from the simple Hamster wheel causing a hamster(or similar rodent) to be stuck in a never ending run over to the innocuous organ grinder. (Active Defense) Catnip, cheese, bones, honey thrown at an animal type to provide a delay in their movements. Other possibilities exist but I leave that up to you.
From the Animal Perspective: I am going to deliberately leave this blank as I am not sure whether you want to anthropomorphize your animals and introduce weaponry as per your link or stay with variations on their natural forms. I would suggest that the former might be necessary or alternatively keep them exactly in the natural forms and attach technology to them. Various counters could be the look of cuteness, PETA red tape forms distracting humans into filling out the forms and not able to attack for a round.
Will come back to this - but off to a phone conference atm.
Further aspects you might look at from a monetisation aspect is the sale of virtual army types. For example a themed army based exotic animals species from Africa or Australia, or Aerial warfare pack utilising birds species, the cute and cuddly animal pack etc etc.
However am really going to stop here as this forum is intended more for aspect of writing in games and not about game design or business related aspects. If you want to chase up either of those issues you should create new threads in appropriate forums. Either way I hope this helps inspire you