The Backstory
When the Odyssey flavor text was being written, one of the writers came up with a character named "Matoc, lavamancer."
The creative team loved the idea of a lavamancer and looked around to find a card that could embody this concept. But none of the available art seemed to fit. Finally, they decided to use a card that could plausibly claim to depict a lavamancer.
Obstinate Familiar | Art by Terese Nielsen
A familiar's got to have a master, right? And the art for Obstinate Familiar has a hooded wizard in it, so that was picked to be the lavamancer. In the next set, Torment, the creative team commissioned some art to be the lavamancer. And they made sure to include the familiar to remind people who it was. Essentially, they moved the camera around to the other side of Obstinate Familiar.
Grim Lavamancer | Art by Jim Nelson
Modern Day
The original Arcana on this topic says, "[T]he Lavamancer never goes anywhere without his familiar." So when new art was commissioned for Grim Lavamancer's appearance as a judge promo, the creative team made sure to include that detail. The card later appeared with the new art in Premium Deck Series: Fire & Lightning:
Jim Nelson | Art by Michael Sutfin
See? The lavamancer really doesn't go anywhere without his familiar!
Anyway, that's the art that was used for the Magic 2012 version. That's the point of all this.