"Don't judge a book by it's cover." This is what comes to mind when I read this post, but I'd just like to mention it would be hard to garner support for a card with bad art, even if the design is good. It's also especially true if the card has relatively simple, non-flashy mechanics. I don't see this as an issue in this community, however, as majority of the forum members are vets and can probably discard the art and simply look at the features the card brings to the game.
However, as a new player myself, I find it hard to understand the idea of the card and I feel less inclined to when I see some random paint image put up as the card art, so art-less cards should be discouraged but still allowed to be put up.
My vote is yes.