You can write your mob suggestions on this page.
Snails and an alternative rabbit to the vanilla version
You should also add some tameable mobs and things to tame them.
How does a mouse or centipede have more health than a chicken? Don't be afraid to make the tiny critters have only 1 heart or even a single health point! Also, if you haven't done this already, tiny critters should be immune to fall damage (as they are in the real world, see Haldane's classic essay On Being The Right Size).
Make some mobs tamable, please.
Orange1861: Can you add cricket repellent? You place it in a area and crickets don't spawn and only crickets receive the wither effect. This would be good because they keep spawning in my building and they destroy my farms.
Orange1861: Worms and Bees would be wonderful additions. Also making animals+ compatible with ExtrabiomesXL, Fun World Gen, Realistic World Gen, and biomesO'plenty would nice.
Not a mob suggestion, but I suggest you add the new mobs in 1.7.10, because I (like many others) use a lot of mods that are still in 1.7.10. I like this mod a lot and I want to use it with my other mods. Thanks! -64M3_4DD1C7 and sky01_
Crabs shouldn't make skeleton sounds.
Crab legs should be cook-able
Ducks should drop duck, not chicken.
Turtles should drop turtle shells and raw turtle.
Birds should fly.
Mice should spawn in the same conditions as bats.
Centipedes and crickets should have animated legs.
Crickets should only chirp at night.
Add a config so I can change the spawn rates of birds, fish, mice, and crickets. (mice and crickets are WAY too common, I can never find birds, and fish should be extremely common.)
Penguins could be bigger.
Mice should scurry if you get too close to them.
Fish should be thinner.
Crickets and butterflies shouldn't spawn in caves.
Guardians should shoot down all added sea creatures.
Bugs should die as soon as they touch the water.
Birds should drop feathers.
Penguins should drop feathers.
Because whales are mammals are not fish, they should drop whale instead of fish.
Crickets, butterflies, and other insects should not be able to trample crops
Crickets should only spawn on grass
Butterflies should spawn around flowers (and should be very common in flower field biomes)
New food items for the tropical fish and piranha (as well as cooked versions)
Shark gills which can be used in replacement of puffer fish for water breathing potions
Badgers that spawn in plains and savannah biomes who will actively hunt rabbits, chickens, ducks, mice, and snakes (they will also go after the player if they get too close or attack) who could possibly drop leather or possibly a hide of some sorts
Monkeys that spawn exclusively in jungle biomes who can (and actively will) raid chests for various food items (watermelon slices, bread, apples, pumpkin pies, etc.) and learn to use doors by witnessing a player character do so
Walruses that could possibly spawn along regular and cold beach biomes that would attack when provoked they could possibly drop some kind of food item (and potentially, though very rarely, a bucket)
Scooby and I are with everyone else on the reducing of spawning of insects, ESPECIALLY crickets. The buggers keep eating all our Scooby snacks, and even when we finally do find a place to hide, we can't escape the "CHIRP. CHIRP. CHIRP. CHIRP". If it isn't fixed soon, I fear we may turn to the dark side.
Oh, and one more thing, if you revise the cricket spawning, please don't just make it for 1.8 version of Minecraft. Please make it for 1.7.10. Please, if you won't do it for us, do it for the Mystery Machine gang as a whole. We promise to never meddle in your business.
I update these suggestions since the last has been refused and I got new ideas. I had thought to new animals to add :
Scorpions : They are agressive only the night and in the darkness like the spiders or when they are attacked. They spawn everywhere in the night.
Rats : They are a bit bigger than mouses and are agressive only the night and in the darkness, or when they are attacked. They spawn in the same places than the mouses but especially in the caves.
Snails and Slugs : Nothing particular to say about them, they advance slowly and are totally inofensive. They spawn in the forests, plains, swamps and jungles.
Bees, Bumblebees, Wasps and Hornets: They spawn the days in small group and foraging flowers. They are neutral and become all aggressive if they are attack and track the player in the same way than the zombie pigmen, but in a really quicker way. They can poison the player. They spawn in forests, plains, swamps and jungles.
Beetles: They are inoffensive. They spawn a bit eveywhere but especially in deserts and savannas.
Mantis: They are neutral and become aggressive when they are attacked. They spawn in the forests, plains, jungles and swamps.
Bears: They are neutral and become aggressive when they are attacked. They spawn in the forests, especially in the taigas. The polar bears spawn in tundras and snowy taigas.
Foxes: They spawn in forest and especially the taigas. They fear the player like the ocelots.
Seagulls: They spawn on the beachs and are totally inoffensive.
Parrots: They spawn in the jungles and totally inoffensive.
Ostriches: They are passive. They spawn in savannas. They tend to put their head in the floor when they are attacked.
Lobsters: They are neutral and become aggressive when they are attacked. They spawn on beachs.
Dolphins: They are passive and tend to turn around the player. They can be trained for travelling the sea.
Stingrays: Brown and smaller version of the manta rays.
Anguillas: They are passive but hurt and poison when they are touched.
Medusas: They are passive but hurt and poison when they are touched.