I find that occasionally an event will occur that the dwarves love so much it becomes a recurring theme in their artwork. Repetition is inevitable, but sometimes they really go the extra mile to include certain images in their art.
The most recent and to me the funniest example I've seen of this was a strange event I wasn't really very clear on how happened. Somehow, the first dwarven caravan that arrived (well one of the wagons anyway) didn't so much arrive at the trade depot as it did fall off the mountain from like two z levels above. The wagon crashed into the depot, sending all the other merchants scattering. I was annoyed at first (I had planned on getting an anvil from that caravan) until I realized all the swag from the crashed wagon was now mine (waaay more than I could afford, including both a steel and iron anvil). For a while my only two military dwarves wore leather and bone armor, except each had one giant ornate steel gauntlet.
So anyway, this happens and it's confusing and hilarious. A little while later, I set my first bit of stone to be engraved. Usually the first image is either the ascension of the mayor or the founding of the fort, but this time it was "a wagon falling". The falling wagon appears at least once in every major series of engravings in the fort, in every noble bedroom, in the dining room, outside the fortress. The time the wagon fell was their favorite thing ever.
Anyone else have interesting experiences with this phenomenon?