I can guess it would be less objective, because, since no one can vote for it's own artwork, people might start to vote for authors with higher rating (just for get an additional upvote from a bigger fish).

Also, I don't know how you can stop friends-for-frienfs votes. Let's see how It would work now and based on this, we could make a conclussions for future

Digital&painting (also I would add craft). - imho, you might allow those works for a contests but make different nominations