Because "Other" isn't strictly an element, you can make it a thin vertical strip running below the other 12 elements. It could be the ground, with assorted weapons and Shards buried in it.
Just an idea.
I think you mean, 'horizontal' strip, or else it'd divide the elements in half or something. ^^;;
Otherwise, I vote for Lyelle's idea, and with Time and Aether, why not have a lightning bolt striking down from Aether's side into Time, where Time distorts the lightning bolt effect with shading (You could also put a person in between the two, on Aether's side walking through an object into Time's world, where you see an older/younger version of the person in question).
Just my two copper.