Plymouth has been working perfectly on my Fedora 10 box after I edited my grub.conf file to match the vga modes required for my display. After upgrade (or fresh install) to Fedora 11, it stopped working again. No idea, what went wrong. Tried digging through the problem and came across the nice guide: http://www.my-guides.net/en/content/view/161/26/2/13/
All I needed to do apart from modifying grub.com was, change the theme to solar from default (text).
su – root
plymouth-set-default-theme solar
/usr/libexec/plymouth/plymouth-update-initrd
Thanks my-guides.net