Well, that used to be the case, that they would send a RFE. However, and I don't have any indication that this would apply to this case, there is a worrisome trend of USCIS outright denying the cases instead of sending RFE in order to clear backlog quicker. I would doubt that they would do that for lack of GC copy and pictures. I don't think USCIS would be very happy if you cancel the checks. I would say, leave it at this, and wait for RFE or go to the interview with the GC photocopy and photos.
Read this Response from USCIS:
http://www.uscis.gov/files/nativedocuments/AILA_28oct08.pdf
"Response: USCIS remains committed to providing customer-oriented service and judiciously exercising its authority to outright
deny applications or petitions. Certain instructions in the cited 2005 Yates memorandum are not pertinent given recent regulatory
changes.
For reasons outlined in great detail in the new RFE rule, USCIS expects the public to provide complete information in each
Form and to include all required documentation with each filing. Incomplete cases take more time to resolve and take time away
from processing cases in the queue that have been properly documented. So while USCIS makes every effort to avoid needless
denials,
USCIS may exercise the authority to deny an incomplete or poorly presented case. What constitutes initial evidence for a
particular application or petition is generally set forth either in the applicable forms instructions and/or regulations pertaining to the
particular classification or benefit sought. As referenced in Mr. Neufeld’s June 1, 2007 memorandum, “The instruction sheet for an
application or petition includes requirements for proper filing of each type of application or petition. Every application or petition,
regardless of the benefit sought, must include complete information in all required blocks, be signed, and – unless the fee is waived
– include the correct fee.” Upon review of the record, if the USCIS adjudicator determines that the applicant or petitioner has not
met his or her burden to establish eligibility for the benefit, the case may be denied."