Here is a guide to install extra plymouth themes from your Synaptic Package Manager. The following plymouth themes can be installed: fade-in, glow, script, solar, spinfinity, text and ubuntu-logo (default plymouth theme)
To install the plymouth themes open your Synaptic Package Manager (System -> Administration -> Synaptic Package Manager) and type:plymouth-theme in the search field. Double click the theme you want to install and mark for installation, when the theme is installed close your Synaptic Package Manager. Now open a Terminal window (Applications -> Accessories -> Terminal: and copy+paste the following line:
sudo update-alternatives –config default.plymouth
A list with installed plymouth themes will appear and here you can select the theme you just installed. Now copy+paste the following line:
sudo update-initramfs -u
When finished close the Terminal window and restart your system to see the installed plymouth theme