Or maybe it was never painted by human hand but instead produced in hell.
I do believe that is exactly it - especially considering the importance the portrait will hold once the plot returns to the present. (One odd thing about the portrait is these eps, though, is the color of her dress is all wrong. And if it's simply the way it's lit, I have no idea how they did it.)
But one thing that's far more important than the appearance of the portrait - and something that I'm quite surprised that no one has brought up - is that this is the infamous ep in which director Lela Swift immortalized the crotch of Joel Crothers/Nathan Forbes in one of the most, uh, unique, or rather notorious segway shots ever seen on DS!!
It's almost enough to make one not even notice that the ep also features more great light/shadow shots: