Welcome to the Fingerpring Kickback Club, and the forum. My class was "all inclusive" and I don't recall being told to sign the photos.If you didn't sign the back of the pics then you'll get them back in the mail to sign.
You wouldn't be the first.
It didn't delay the process much longer. It does seem like it takes foreever. Soon enough you will be checking the mailbox and DPS status web site on and hourly basis.