That is a period-accurate Assyrian throne the king (or governor, probably) of Nineveh is sitting on, which looks a bit like a padded footstool and is decorated with carved animal heads. You have to hand it to him, he's decisive. You say some Jew is delivering a vague prophesy of doom? EVERYONE STOP EATING, RIGHT NOW. "But Your Majesty, he didn't even say to do that." "Which one of us is the king? And that goes for sheep too, the sheep have to fast. And put sackcloth on them." "On the sheep?" "Did I stutter?"
Actually, being as how sackcloth was usually made of animal hair, the idea of putting it on the livestock is even funnier than I originally realized. You, put a bag on that goat, you wanna destroy the whole town?
The irony here, of course, is that Jonah is the most successful prophet in the Bible, when what he really wanted was to fail!