Improved Familiar - Beheaded. What can it do?

[chaoseffect]

A Beheaded is a low level candidate for Improved Familiar, but take a look at the extra abilities they can have. My question is can your Improved Familiar version get those as well, and if so, when and how?

I'd say it would be reasonable to say yes, but you need to keep to the Familiar CR to Caster Level pattern already in place (CL 5 = up to CR 1, CL 7 = up to CR 2). That said, I was wondering if there was a RAW explanation as those tend to go over better with less discussion.

Someday I want to play a guy who carries around a sack filled with a swarm of flying severed heads.

[lantzkev]

for a familiar it would only have the "stock' that you see without any extra abilities.

For creating one, you'd go with create undead rules etc.