Kled
So, I'm just looking at possible lore events or reasons for why the posters were made for the lizard beast.
In all three posters, Kled signed his name at the bottom, speaking of his beast mount. We can assume the creature in question is a beast mount because of Kled requesting a saddle for the beast.
The first picture mentions of how his beast mount is a coward, forever running. Chances are, this creature just isn't the "bravest" of monsters ridden into battle. The fact that Kled mentions the cowardly beast hid in a bush means that it rather live than to fight anything.
However, in the last picture, we see Kled referring to the lizard as "Pride of Noxus". This is most likely because the beast possibly did something grand (albeit on possible accident) to cause Kled much pride. Remember, in Noxus, you must earn respect. You are weak and cowardly otherwise. The creature hasn't earned its respect until "The Battle of Bucket Creek". Maybe the creature did something on its own and defeated the enemy at their base, alerted everyone of danger, defended a high commander and brought him back alive, or something completely ridiculous that happened on accident.
Either way, Kled had a new change of view for the Frilled Lizard.