Hi, I want to have a "DONT PANIC" boot screen of my iliad :)

is it possible ?

As far as I know, is not possible. See this thread.

http://forum.irexnet.com/viewtopic.php?t=1535

The boot screen is not exchangable, but you can edit the PIN background image. The file is located at /usr/share/contentlister/pincode_lock_background.png

Just configure the iLiad to ask for the PIN after booting, and you can supply your own image.