The location of grub configuration file in Cent OS is /boot/grub/grub.conf. You can edit it manually using any text editor.
You can specify the image to be shown at grub prompt but I am not sure if it supports animations. To specify the image you can use splashimage directive in grub configuration file.
Last edited by linuxlover.chaitanya; 04-25-2012 at 11:27 PM.