I actually think art can be a distraction when judging a card at its early stages. The true importance of adding a new card is improving the game. Whether that's through new mechanics, a counter balance, etc.; how the the card functions should be the primary concern at first. Sometimes people vote based on the art, or the art influences their voting, when really it is the effect of the card on the overall game that matters most. The art will matter when it comes time to put the card in the game, but that should come at a later stage, when the function of the card is ironed out and the art can best reflect the final form of the card.
tl;dr Art is a distraction at early stages. Focus on the mechanics. Bring in the art later when it best reflects the card after iteration.