How do I customise my Plymouth theme?

I want to update my splash screen (when I boot or logoff), logo etc... to use the solar theme.

I did:

sudo apt-get install plymouth-theme-solar

then I went to the themes folder to customize it:

/lib/plymouth/themes/

and I updated logos and other images:

sudo update-initramfs -u

I think this command is the right one to run but when I run it, nothing is updated

What am I missing?

This should do the trick:

sudo apt-get install galternatives

sudo galternatives

Then select your theme from key default-plymouth and do the update-initramfs -u again.