From Ren'Py

Preloader Image

To create a Preloader Image (placeholder image show while Ren'py is reading the scripts and launching the game), make an image named presplash.png, and put that image into the game directory.

Note: Ren'Py takes longer to load the first time after the script changes then it does later on. Game should be run twice in a row to see how long it takes the second time.