One of the things that slow down K-1 Fiancée visa applicants is getting the passport photo and signatures from the alien fiancée abroad. Back on November 1 2005 the USCIS released a memo to it's Service Center Directors instructing them not to issue an RFE (Request for Evidence) for a K-1 petition that is missing the alien's photo or signature on the G-325A. The memo further instructs the directors not to issue an RFE if the sponsor did not sign his/her G-325A.
Unfortunately, there is one other document that the alien fiancée is required to sign and that is the Fiancée Letter of Intent. Some petitioners have reported being approved without the alien's signature on the Fiancée Letter of Intent but there is no clear directive indicating this signature is not required.
The best way to move as quickly as possible through the Fiancée Visa process is to submit a petition that is complete and professional. This means including the alien fiancée's signature and passport photo whenever possible.