It can be any scribble. Signatures don't necessarily spell names. My signature is a scribble for 20+ years now. As long as the new citizen keeps using this signature in all official documents, it's OK. But if person keeps switching signatures, it can be a problem. How does she sign her driver's license in the US, foreign passport, lease agreement, employment docs, medical papers for doctor? Just use the same signature.
Example of a scribble here:
Do you think anybody can read this? And this is acceptable. It can be anything as far as I know.
My field office gave out certificate and let us sign it at home.