Quote Originally Posted by enderlord99 View Post
That's up to the DM, but only living creatures can become Liches, and Liches aren't living creatures, so a Lich can't become a Lich. Basically, taking a template will sometimes prevent you from taking that same template again... but only sometimes.
Yeah, I just checked and the lich template can only be added to humanoids and it changes the creature type to undead. However I did find a fun template that doesn't change creature type...

Lycanthrope