Yes it does work for x64, I am running 64-bit. I haven't tested it specifically for 9.04 yet, but it works for 7.10, 8.04, 8.10. And probably 9.04
I got splashy working for quite some while now. first of all I install splashy
After that I create my boot splash from a picture or I set an existing one.
sudo apt-get install splashy splashy-themes
To set one (after creating one you will still need to set it):
sudo splashy_config -c
Now I need to add the vga=791 (791 = 1024x768, I use this for compatibility with older PCs, change as desired) to my grub.
sudo splashy_config -s <name of theme>
sudo nano /boot/grub/menu.lst
kernel /boot/vmlinuz-2.6.27-11-generic root=/dev/sdc1 ro quiet splash
Now the most important before we reboot. Let's update our initramfs to hold our image so Splashy will work.
kernel /boot/vmlinuz-2.6.27-11-generic root=/dev/sdc1 ro quiet vga=791 splash
After 1 or 2 reboots Splashy should work, it did for me. I hope this helps.
sudo update-initramfs -k `uname -r` -u