Mods are an integral part of World of Warcraft. The PBS has a few mods already.
Here are the Mods you will want to have while hunting and fighting in the Pet Battles.

Pet Battle Quality is a Mod that will show you the quality of the wild pets you are fighting. This is a great mod to use if you are an avid pet collector. When you enter the battles, the Mod will change the color of the names of the pet to reveal its quality. Grey = Poor, White = Common, Green = Uncommon and Blue = Rare. This also works on the player Pets in PVP.

Pet Battle Teams is a Mod you will want to use to level up your pets. This Mod allows you to make 60 different teams of pets. Use this Mod because the Revive Pets spell has a 8min cool down. Within those 8 minutes, there are places where you can have a lot of battles. Swapping teams in a timely manner will shorten your Pets leveling time.

Pet Journal Enhanced will help you choose what stats you wish your pets to have by adding a circle with an shape on the lower left side of the Pet icons in your Pet Journal.
Heart = More HP
Arrow = More Speed
Sword = More Attack Power.
If a Pet doesn’t have an icon it means that its stats distributed evenly.
This Mod also give more sorting features that the plane Pet Journal doesn’t have.

GupPet while not being a Pet Battle Mod does have some fun Pet features. You can have the Mod summon random pets/mounts where every you go. It has active buttons to press (that can be hidden) or you can use Key-bindings.