cd /usr/share/plymouth/themes/
mkdir mytheme
cp xubuntu-logo/* mytheme/*
cd mytheme
sudo mv xubuntu-logo.script mytheme.script
sudo mv xubuntu-logo.plymouth mytheme.plymouth
sudo nano mytheme.plymouth (Change path and filenames)
--- Change logo.png & logo_16bit.png & mytheme.script
sudo update-alternatives --install /usr/share/plymouth/themes/default.plymouth default.plymouth /usr/share/plymouth/themes/mytheme/mytheme.plymouth 100
sudo update-alternatives --config default.plymouth
sudo update-initramfs -u