Not sure what I'm missing here, but the launch screen works fine on every device but iPad Pro. The launch screen is indeed a storyboard. It actually works perfectly fine on the iPad Pro simulator.
Any suggestions?
Update:
Ok, so I've added a tileable image to xcassets. There are three sizes. No matter how I slice it, it always shows up as expected in the storyboard and the simulator, but it never renders on device. Frustrating!