In Apple's Human Interface Guidelines, they suggest that the launch screen should match the first screen of your app. In the example they give, the only parts of the launch screen are the non-dynamic parts (the UI around the web content).
Design a launch screen that’s nearly identical to the first screen of your app. If you include elements that look different when the app finishes launching, people can experience an unpleasant flash between the launch screen and the first screen of the app.
The launch screen is presented before your app loads, and it should be used for static content only.
If there are any UI elements around the image that is displayed, show those in your launch screen. If not, choose a neutral background color that works well with the theme of your app.