Setup plymouth using icewm -- how?

"To configure plymouth, that is to choose and install the preferred boot theme, the user has to invoke plymouth-set-default-theme..."
Please see the following link for details:
http://manpages.ubuntu.com/manpages/lucid/man8/plymouth.8.html

Also see http://ubuntuforums.org/showthread.php?t=1440101

mike@Hinote:~$ sudo aptitude search plymouth
[sudo] password for mike:
p libplymouth-dev - graphical boot animation and logger - development files
i libplymouth2 - graphical boot animation and logger - shared libraries
p lubuntu-plymouth-theme - plymouth theme for Lubuntu
i plymouth - graphical boot animation and logger - main package
i A plymouth-label - graphical boot animation and logger - label control
v plymouth-theme -
p plymouth-theme-fade-in - graphical boot animation and logger - fade-in theme
p plymouth-theme-glow - graphical boot animation and logger - glow theme
p plymouth-theme-kubuntu-logo - graphical boot animation and logger - kubuntu-logo theme
p plymouth-theme-sabily - plymouth theme for Sabily
p plymouth-theme-script - graphical boot animation and logger - script theme
p plymouth-theme-solar - graphical boot animation and logger - solar theme
p plymouth-theme-spinfinity - graphical boot animation and logger - spinfinity theme
p plymouth-theme-text - graphical boot animation and logger - text theme
i plymouth-theme-ubuntu-logo - graphical boot animation and logger - ubuntu-logo theme
i plymouth-theme-ubuntu-text - graphical boot animation and logger - ubuntu-logo theme
p plymouth-theme-ubuntustudio - Ubuntu Studio Plymouth theme
p plymouth-x11 - graphical boot animation and logger - X11 interface
p xubuntu-plymouth-theme - Plymouth theme for Xubuntu
mike@Hinote:~$
mike@Hinote:~$ uname -a
Linux Hinote 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC 2010 i586 GNU/Linux
mike@Hinote:~$
mike@Hinote:~$ sudo plymouth-set-default-theme --list
sudo: plymouth-set-default-theme: command not found
mike@Hinote:~$

Where can I find plymouth-set-default-theme ?
N.B. If it makes a difference: I am running icewm not Gnome

Please check the link from my second answer - there you have additional commands that will allow you to change the plymouth theme under command line.

mike@Hinote:~$ sudo update-alternatives --install /lib/plymouth/themes/default.plymouth default.plymouth /lib/plymouth/themes/mythemes/mytheme.plymouth 100
update-alternatives: error: alternative path /lib/plymouth/themes/mythemes/mytheme.plymouth doesn't exist.
mike@Hinote:~$

mike@Hinote:~$ ls -al /lib/plymouth/themes/
total 20
drwxr-xr-x 5 root root 4096 2010-04-28 14:17 .
drwxr-xr-x 4 root root 4096 2010-04-28 14:17 ..
lrwxrwxrwx 1 root root 34 2010-04-28 14:17 default.plymouth -> /etc/alternatives/default.plymouth
drwxr-xr-x 2 root root 4096 2010-04-28 09:34 details
lrwxrwxrwx 1 root root 31 2010-04-27 19:43 text.plymouth -> /etc/alternatives/text.plymouth
drwxr-xr-x 2 root root 4096 2010-04-28 14:17 ubuntu-logo
drwxr-xr-x 2 root root 4096 2010-04-28 09:35 ubuntu-text
mike@Hinote:~$

What must I do to create the missing directory/file ?

That was just an example, not a ready solution.
You should have read it before running it.
You need to adapt the commands to your theme names.

That was just an example, not a ready solution.
You should have read it before running it.
You need to adapt the commands to your theme names.

Sorry, my bad.
I did not realise that <mytheme> was a variable.

(cf. http://alpha.mike-r.com/jargon/M/metasyntactic-variable.html )

Thanks -- All OK now!