Yes, edit menu.lst as root to change your splash image. This is the line to change
Code:
splashimage=(hd0,0)/grub/splash.xpm.gz
Edit /etc/fstab to make a partition rw. Add rw to the options
Code:
/dev/hda450 /example auto noauto,user,exec,rw 0 0
I don't know where you can download the image files. Try Googling.