The art team created a number of lovely new icons for hunter pets in early MoP (or was it late Cata?) but they were never implemented. They're just sitting in the game database unused. These were for ones where the current icon either isn't the right beast at all (like basilisks and shale spiders) or is a beast with riding harness or something.
We've requested for them to be implemented a few times now, but nothing has ever come of it. Maybe WoD will finally be the time!
I've posted a reminder request here:
http://us.battle.net/wow/en/forum/topic/13086799039#1
UPDATE: Sorry, you need to be be flagged for the beta in order to post
If any of you have a moment to post in support it'd be much appreciated
No rush; if posts appear over a longer time period at least it'll be bumped now and then
Maybe someone will see it and care.
Thanks
FYI, the icons are:

Basilisk: inv_pet_basilisk

Crane: inv_pet_crane

Direhorn: inv_pet_direhorn

Goat: inv_pet_goat

Dog: inv_pet_mastiff

Monkey: inv_pet_monkey

Shale Spider: inv_pet_shalespider