When you start GIMP, you see the splash-screen displaying short status messages while the program is loading all its components.

Of course, you can customize the splash-screen: Create a splashes directory in your in your personal GIMP folder (/home/user_name/.gimp-2.6 on Linux, C:\Documents and Settings\user_name\.gimp-2.6\ on Windows).

Copy your image(s) into this splashes directory. On start, GIMP will read this directory and choose one of the images at random.