[coreboot] Beginner Information - What can be a payload?

[Rafael Send]

Hi,
Total beginner here. In fact, I'm just researching interesting
possibilities for using this and how coreboot works.

In particular, I'm wondering how to create custom payloads, and what sorts
of things can be payloads.

According to the wiki, the target file for a payload is an ELF file.
However, I'm not clear what can be turned into a payload. The wiki also
says that entire (small) Linux distros can be made into payloads (and
SeaBIOS can use floppy images),  but I'm unclear on what this means and how
to do it.

For example, if I wanted to turn a TinyCore Live CD into a coreboot
payload, could that be done? TinyCore copies itself to RAM and doesn't
require write access in that mode, so as far was what the distro expects
that would be compatible.

Are there any resources or articles I can read that would provide more
detailed information about this subject?

Cheers,
R