The default image includes a splash image that displays the TS logo. You can replace this with your own logo by replacing the files in /ts/splash/, or disable the splash screen by removing these files. The fbsplash utility that displays the splash logo in a ppm format. You can use graphics applications such as Gimp which can export to ppm, or you can use imagemagick in Linux to convert another file to ppm:
convert splash.png splash.ppm
The image resolution usually should match the screen, but otherwise it will be aligned to the upper left corner. If the system is configured to automatically boot to Debian it will display the splash screen until X11 is started.