Let me rephrase my suggestion.
Design a vanilla creature to be put into the game.
I think what Frozen's trying to say is that given the amount of vanilla creatures in EtG's main cardpool already, could we really put in new vanilla creatures without a) causing some kind of redundancy in EtG's current card base and/or b) filling a niche that a creature with an ability would've done better? Massive Dragon is an existing example of this redundancy problem - Chargers tend to be much more efficient attackers and Titan/Armagio are much more practical to fling at the opponent.
For a different card game example, compare relatively recent releases of Normal Monster Yugioh cards - you rarely see completely vanilla cards nowadays unless they're introducing a new type (Shining Knight, Mandragon, and Doradragon are the only truly vanilla Pendulums - every other Normal Pendulum Monster has a spell effect, Metaphys Armed Dragon was used to introduce Wyrm, etc...) or have a combination so unusual that it's allowed to get away with it (Labradorite Dragon is for all intents and purposes vanilla, but it's also the only level 6 Tuner Monster to exist.) EtG on the other hand doesn't have the luxury of constantly getting game-warping mechanics that change the face of the game and allow new spins on vanilla.
As a second example: MtG has a very common tendency to reprint very similar vanilla cards each block (e.g. there are a ton of Grizzly Bears variants out there), but it gets away with this because it can 'reset' its card pool through the block system. However, EtG draws most of its cards from a bazaar where all the cards remain available, so additional vanillas don't seem to serve an good point here.
Mind you, I'm not trying to say it's a bad idea, but I do want to try and explain why it may be a tough to make a feasible challenge. If there's a good reason that could really get people's gears grinding and designing vanilla creatures that do something fresh, I'd be in favor of making this challenge happen.
