From Ren'Py

Splashscreen Effect

An example of a splashscreen effect can be found at the end of the "script.rpy" file in the demo/game directory of Ren'py :

# The splashscreen is called, if it exists, before the main menu is
# shown the first time. It is not called if the game has restarted.

# We'll comment it out for now.
#
# label splashscreen:
#     $ renpy.pause(0)
#     scene black
#     show text "American Bishoujo Presents..." with dissolve
#     $ renpy.pause(1.0)
#     hide text with dissolve
#
#     return

To add a text splashscreen to your game, insert code like this into anywhere in your script file (as long as it is not itself in a block):

label splashscreen:
    $ renpy.pause(0)
    scene black
    show text "American Bishoujo Presents..."
    with dissolve
    with Pause(1.0)

    hide text
    with dissolve

    return

Here's another example of a splashscreen, this time using an image:

init:
    image splash = "splash.png"

label splashscreen:
    $ renpy.pause(0)
    scene black
    with Pause(0.5)

    show splash
    with dissolve
    with Pause(2.0)

    scene black
    with dissolve
    with Pause(1.0)

    return

You need to declare the image in an init block (which can be anywhere in your script file, either before or after the splashscreen code). You must also declare another interaction before the scene transition, which is why $ renpy.pause(0) must exist as the first thing in the splashscreen label.