These days, LinuxBIOS expects to find a bootloader in ELF format at the beginning of the ROM. Etherboot has an extension to load an image from a raw IDE partition. I'm working on one that can handle an ext2 filesystem, but it's VERY alpha at the moment.
Actually Adam has that patch already. His patch supports ext2, ext3 and vfat at the moment. Shouldn't be too hard to support other filesystems also since most of the code can be extracted from grub.
-Andrew