Oh I see, I was mistaking snotlings for those things goblins sometimes ride.
Thanks for the answer about the models though
Those would be Squigs, or 'Squiggly Beasts.' They're a collection of various related animals, though the most common is basically a mouth on legs. Orcs and goblins use them as war beasts, and some night goblins are drug addled enough to try and ride them into battle. Most such goblins are eaten in short order, but a few survive long enough to actually get to the fight, and if someone manages to survive the battle without being bucked off and eaten they get a lot of respect from the other goblins.
Other squigs include hairy squigs, used by orcs as living wigs, giant cave squigs which can grow to prodigious size, a breed for eating which I think was just called tasty squigs, and the mighty Squiggoth, which is a four legged dinosaur sized monstrosity.
Night goblins, who mostly live underground and take lots of drugs, are the foremost users of squigs in battle in WHF, being the inventors of the Mangler Squig, two giant cave squigs chained together, poked with pointy things until they're really mad and then sent whipping each other about in the general direction of the enemy with an awkward random movement, because squigs move by hopping and having two tied together results in a very bumpy trip for both of them.