Changing the boot/startup theme of ubuntu live cd

[neurobin]

Customize the plymouth theme in /usr/share/plymouth (xubuntu 16.04) or /lib/plymouth (xubuntu 14.04).

And, to apply this changes, when JLiveCD asks for

......have you modified init script or kernel module? (y/n)?:

give it 'y' so that it rebuilds the initrd