I'm sorry for bad english in future text. Im also sorry if this was disscused already but i have to try with this idea.

I think it would be nice to have some kind of wild animals but that animals should be living in forest and could be agresive or neutral,if they are agresive they would attack any shinobi they see near that animals should be wolf,tiger,bear,snake,gigant spiders,gigantic birds (gigant eagles and hawks,etc.),crocodile,wild cats,big lizards,sharks,stingray etc. And peacefull animals like deers,cows,pigs,chicken,peacefull insects and birds,delphines,wheals and stuff like that.

But there would also be beast that have unique looking and are living in special places like mountains,forests and oceans,special beast place inspired by mountain monbyoku (toad village) and that places would be really hard to find. So those beasts would be:

Gigantic cobra snakes
Gigantic wolfs with 2 tails
Gigantic Squirrels that can be warriors IMAGINE THIS
Big Eagles
Big Lions
Big Bears that can be warriors
(if needed i could make an idea about their hidden villages too)

And there would be Shinobi animals that are cats,dogs,smal hawk's.

Animals can be killed for meat and stuff for making your outfit and stuff like that (crafting)
Beasts can be knocked down and sealed in scrols then used in fights (1 time then scrol disappears) or you can make blood contract with them and can summon them to aid you in battle for few seconds (attack the enemy that attacks you or the target that you attack (land hit on) for 15/30 seconds the disappear and have cooldown of about 5 hours (you decide) or you can use them as mount to travel faster (Eagles to fly on them) and ride them for about 1/2 minutes then have cooldown of few hours,when you have contract you can summon them after cooldown dissapear,if you have sealed them in scroll you can use them just once.

I will be happy to see your opinion about this in reply. Thanks for reading.